I decided that I wanted both onboard air and an onboard welder for my '76 FJ40.   There are a lot of ways to do this, but I didn't want to spend too much money, so I decided to try a combination of a junk yard York compressor and running my stock alternator with a separate junk yard Ford 105 - 130 amp alternator to do light duty welding.  The other design consideration is that I didn't want to rearrange everything irreversibly so that I could return it to stock configuration if need be.

First start with a mid 70s to mid 80s Volvo York compressor and mounting bracket.  This was $17.50 at the local Pick N Pull.  Get the associated hardware, hoses and belt tensioners.  Be sure to get one with the double pulley.  The tag number should contain the ID# 210R somewhere in the number.  Here is what it looks like:
Front side:                                                        Rear side:

 

Remove the bracket.  Cut off the front part of the bottom of the bracket shown in the foreground of the picture below.  Also cut off the Saginaw P/S pump mounting brackets and bushings off the top of the bracket.

When you are done cutting the bracket, it should mount on the compressor like this:

 

Here is the way the stock alternator is mounted on the 2F:

 

In order to make room to mount the stock alternator in the same location and still have room for the second alternator, we need to mount the compressor horizontally, with the pulley facing away from the engine.  Contrary to commonly held beliefs, the manufacturer says that it can be mounted either vertically or horizontally.  The manufacturer recomments that the suction side be mounted above the discharge, but this is evidently specific to its use in air conditioning rather than making any difference on the amount of oil the compressor pumps out.  I tested the oil output in all three orientations and the amount of oil discharge were the same. This means that you also have to move the battery tray back about 2 inches.  Remove the battery, remove the 4 bolts that hold the tray to the bracket, flip the tray 180 degrees to move it back 2 inches and then reattach the tray witht he bolts.  Next, position the compressor and bracket to test the fit with the other components of the engine.  I used a piece of 2x4 on the battery tray to space it up.  I found that it needed to be spaced 2.5 inches away from the mounting point on the head.  Use a 1/2 inch metal rod or wooden dowel in the pulley groove to line up the pulley on the compressor with the crankshaft pulley.

The next step is to trace the mounting holes on the head onto a piece of paper.  Your dirty fingers will work.  This pattern will be used to locate the holes on the bracket that will be used to connect the Volvo bracket to the 2F head.  A short piece of 2.5 x 5 x 3/16 wall rectangular box tube will work well.  I ended up using a piece of 2.5 x 2.5 box square tube with a piece of 2.5 inch angle stock, since I had this on hand.  Be sure to flip over the paper pattern before you mark the location of the holes.


 

Line up the compressor and bracket on the adaptor.  Check that the pulleys line up exactly and that the bracket is square with the engine.  After double checking, clamp the pieces together and then either tack weld it or bolt the pieces together.


 

I suggest that you take a few minutes to modify the compressor so that is doesn't pump so much oil out.  The York is designed to pump oil to the seal via a loop from the pressure side through the crankcase, to the seal, to the suction side.  You don't really need or want this oiling system when you are using the York as an air compressor.  It is the oil entering the suction port that is responsible for a lot of the oil that blows out of the compressor.   In order to plug this oil port, you need to remove the front seal from the compressor.  Remove the pulley and the magnetic clutch coil.  Then remove the 6 - 1/4 inch hex head screws from the seal retainer, remove the retainer and seal.  Check the compressor manual if you are not familiar with these operations.  The manual can be downloaded from:
 York compressor service manuals
The oil hole is 5/32 inch in diameter.  Cover the bearing with several layers of towels.  Plug the hole with a wad of paper towel shoved about 1 inch into the hole to keep metal chips out of the suction port.  Drill and tap with a 10-32 thread tap.  Carefully blow our the metal chips and cover the outlet and blow compressed air into the inlet to blow the paper towel plug out of the port along with any remiaining chips.  Brush out any remaining chips and then remove the towels.  Put a drop of blue locktite on a 10-32 x 3/8 plug or set screw and tighten it into the threaded hole.

After double checking the fit and alignment, finish welding or bolting the bracket togeter and mount the alternator on to the top holes on the compressor that are closest to the engine.  The alternator mount and the tensioner can be made from angle stock and either welded or bolted together.  I used one of the tensioners from the Saginaw pump on top of the Volvo York compressor to tension the alternator belt.


 
 

Bolt the bracket and compressor into place.  Measure around the pulleys with a 1/2 inch tape measure and get the appropriate drive belt.  Here is the way it looks when the compressor and alternator are mounted.  The original alternator clears the closed hood by about 1 inch in its fully extended position.  Notice the unused pulley on the  compressor.  This will be used to drive the other alternator to be used for welding, which will be mounted just next to the original alternator.

 
 

I also mounted a brace from the top of the motor mount to the bottom of the compressor. The surface of the motor mount is 20 degrees from horizontal.  The brace is made from 2 inch angle stock.  This may be overkill, but there is going to be a fair amount of weight hanging off the side of the head, and I wanted it to be solid.

 
 
 

Next:  Mounting the second alternator for welding.  This is just like the "option two" On-board welder described by Jeff Fretwell in his tech article on the Pirates of the Rubicon web site:
 Jeff Fretwell's On-board welder tech article.
I looked all over the Pick-N-Pull for a 105A or 130A alternator, but all I could come up with is a 90A large case Ford alternator from a 1982 Lincoln Continental.  I didn't want to go home empty handed, so I took it home for $15.  It had a rebuilders sticker on it that said 90A and it looked pretty clean.  I also brought home the belt tensioning arm for the same alternator.

 
 

I added a mounting point on to the bracket for the OEM Toyota alternator after lining up the pulleys and checking the fit under the hood.  I used two 3 inch pieces of 1.5 inch x 3/16 angle stock and I welded them on to the other bracket (although they could also be bolted together).

 
 

I also made a bracket to mount the belt tensioner that bolts to the bottom of the compressor.  It is made of a 5 inch piece of 2 inch x 1/8 angle stock.  I measured the diameter of the belt required (27.5 inches) and went to the parts store and bought it.  then I mounted everything.

With the belts tight, everything fits nicely under the closed hood with about 1 inch to spare.  I don't plan on leaving it mounted all the time and I expect to just mount it when I need it.  In order to wire it up, I ran a piece of 18 ga wire from the ignition + side to a switch and then to the field pole.  It is a simple on-off switch.  For just trying it out, I used some 4 ga jumper cables, but I plan on running a stinger and ground clamp on some real welding cables.  Amazingly, it worked very well but not surprisingly, it did not put out as much amperage as my 250A Linde Tig/Stick welder.  It takes enough horsepower to puwer up that the engine slows noticably when you strike an arc.  I could easily run 3/32 6011 rod at an engine speed of 1,500 RPM.  It will also light and run 1/8 inch rod at 2,500, but it takes a lot of control to keep it lit.  The duty cycle must be pretty good as the alternator case was not any hotter than the stock alternator that is only charging the battery after burning two 3/32 rods.
Here are a couple of examples of stringer beads:  The top bead is 3/32 6011 at 2,000 RPM.  I could easily burn through 1/8 inch angle stock, so penetration should be no problem.  The bottom bead is 6014 fast fill rod.  Obviously, I need to practice with a stick more.

 
 

I'm pretty confident that the Ford alternator could be used to charge the battery if the Toyota alternator failed.   All you would need to do is hook up the B+ and field wires from the Toyota alternator to the same terminals on the Ford.
I also noticed that the alternator easily puts out 120-150 V DC at full field.  This will run most brush type motors, like a 4.5 inch angle grinder and resistive loads like incandescent (but not fluorescent) light bulbs.   This is also high enough voltage to be a shock hazard, so use appropriate care.  I may decide to wire up a outlet box to plug in electrical tools.  It would also be very nice to have a manual cable throttle to control engine speed, as this is the way you control the alternator output.  As an interesting note, all alternators produce high frequency DC and the frequency increases with engine speed.  This seems to be quite a sales point for the commercial on-board welder vendors, but the $15 Ford alternator also puts out a high pitch audio whine from the arc as well.
 

Next up:  Plumbing and wiring the air storage tank and cleaning up any loose ends.