Regarding the 1 1/8" on that trans setup. That is just what the "short" bell housing gives you. It just conveniently matches 3 pieces of 3/8" plate. The center plate has holes for the bolt heads (bolts point backwards on the trans-side plate, forwards on the engine-side plate). The bolt heads can't be over 3/8" tall (I've had good luck with ground down hex or Allen bolts). Leave "ears" sticking out around the bell housing, enough to bolt the three plates together as one, when the trans mates to the engine. Depending on your pattern, you may have to rotate the trans slightly off vertical to get enough bolts working (just bend the shifter in a press....it'll still work).
You may need to hit the bearing store to get a pilot bearing that fits your crank and the R150 input shaft end. I used a rear bearing from an old alternator, that just happened to fit.
You can put your starter bolt threads into the engine side plate, or the center plate, BUT DON"T DO BOTH! The bolts will bind. Carve out of the trans plate/bell housing as necessary for the nose of the starter.
Important step: You MUST take the FWD flywheel and clamp it on a stool. Then go around the teeth (on your new "starter side" with your right angle grinder and a fresh "flap sand disk" (about 120....don't use the coarse grit or the bendix teeth can hang). You will be making a "ramp" or slope for the bendix to clear as it approaches the square face on the back of each flywheel tooth.
The FWD flywheel has the "relief tooth slope" on the wrong sides of the teeth. It won't matter, because you'll probably be driving from the other side of the gear (no you CANNOT just flip the gear...the slope's on the wrong side of the tooth...I tried it...like a dummy).
This cut is NOT critical...you are just giving the bendix teeth enough room to start walking into the flywheel teeth. After grinding the slope, take a round bastard file and file the bottom groove of every tooth on the flywheel. The gears are stamped and the teeth will be too tight on the old "back side" when your starter is engaged (to what is now the new "front side"). It will engage, but it won't disengage if you don't do this. Again...it is not critical accuracy and doesn't take very long. I did this whole process in about 45 minutes on Richard Reed's V4F/SR last August, when we discovered we couldn't actually start the engine!
If your design requires the original starter orientation (from the back of the bell housing) carve out enough of the original truck bell housing to provide mount area against the bandsawed plates (you'll need to make up a spacer block, probably). Make a big enough hole in the engine-side plate that you can see what you're doing when you set the bendix gear engagement...and to check for clearance as described above.
I'm going to offer an opinion, here, to respond to folks who think it's not reasonable to carve out part of the bell housings: Most of the rigidity issues related to bell housings are happening BELOW the line of the bottom of the block. If you'll add stiffeners below that line (up to the sides of the block), you can carve some pretty big holes higher up, and get away with it.
In addition to torque, the bell housing is designed to handle two primary loads....bending forces from road shock, etc., and bending forces from rocking couple vibration in the powertrain. We aren't dealing with huge jumps and bumps (we hope) and we spend a lot of time at very high engine RPM which is outside the range of the largest rocking couple flexure of the powertrain. The rocking couple flex issue is bigger than most people know, and is the reason for added brackets commonly seen on large 4-cylinder engines (nowdays the blocks are made much "deeper" to contain this at lower cost/fewer parts).
Dan and I ran the Getrag 6-speed behind our little 4-cylinder with NO rear trans mount. We fully supported the (carved) bellhousing on our motor plate (with only one bolt hanging the starter). In 1998 I spun the driveshaft at 9400 RPM (in overdrive) on the second half of the record run (the car had 4.11 rear end and the 1/4 speed was over 177). We had no problems with anything moving or touching, despite less than 1/8" clearance between the forward U-joint and the enclosure tube. Also...we couldn't use all the bolt holes, due to "too close alignment". It never was a problem, but we had 2 drive dowels taking the torque loads...not the bolts.
That trans is still healthy and now living in a Twin-Turbo Supra drag car (with part of the bell housing still carved away and missing a bolt)!
Hope this gives you some useful ideas. Regards, JimL
