Aasco flywheel works with stock everything, so I went with that since I already had it on hand and it's not overly lightweight. Everything came together nicely
Engine is complete as a unit and united with the subframe. Car lifted up super high, you need about 33" of clearance not including whatever you're using to slide it under the car. I used low profile jacks to pivot it into place. Then grabbed the engine from the top using an engine crane, and pulled it up into place so I could mate the subframe to the body.
I pulled out the stock return line and got rid of the plastic fuel feed running through the cabin. I used new 5/16" stainless to bend up two new lines for both feed and return. These I flared on both ends, and I very guiltily made a new hole for the return hose to pass through. Even though I am using nice reinforced and jacketed line, I lined the new hole with some thick heater hose to protect the return line. The unused return is capped using the ol' bolt in a piece of hose trick. The new return flows through the e30 m42 fuel pump to avoid a potentially dangerous static charge build up.
After mocking up several times and then coming to realize that I could not access the pin that links the selector rod and selector joint together, I gave up. Instead of shortening the e21 platform, I chopped it down to basically just the cup and immediate surrounding area. Using 3 of the e30 airbox bushings, and cutting down the e21 foam (it has a metal core) I made essentially a mostly-rigid chassis mount. This eliminated a bunch of extra parts and chances for play, and I generally like a more positive feeling shifter assembly anyways.
Since I can't use the stock airbox, obviously we have to go aftermarket. I went with the KA Motors intake kit, as it seems nice enough and comes with an AFM adapter. (I have recently learned the intake is really just a generic piece you can online anywhere for pretty cheap.) While the intake is okay, the adapter is quite the opposite. The AFM adapter is metal and the hole pattern is close enough, but the mating flange was fairly warped. It took about 20 minutes of sanding by hand (with 3 steps of grit) on my work bench to get it flat enough for me to be happy. The "gasket" is made out of a hard, thick, non-malliable material that seems like Polystyrene or something similar. Also WILDLY warped, and since it's completely non-conforming it's essentially useless as a gasket. Ended up sanding this flat enough to use as well, but used some gasket maker on both sides of it.
AFM coupled with Jakeb's bracket. The bracket was pretty rough, and also needed a lot of sanding in certain places to not cause notable hazard to soft hands.