I have more information (talked to a dealer tech), and also a question. Question first, info in a moment.
1. Question: I found a running tbi motor I can pull for $200 or so, but it is in an automatic. Am I correct in assuming I can put a motor from an automatic in my 5-speed? (Aside from swapping a flywheel/clutch/pressure plate into where the flexplate was?)
I forgot to ask the dealer tech about this while I was there.
2. Regarding MPFI into an SPFI: the tech I spoke with seemed very knowledgeable about the EA82. I was impressed, considering the EA82 is probably quite a bit older than he is! He said the cylinder block is the same, but the air intake holes on the MPFI head do not work with the SPFI intake manifold (the intake holes are different shapes). There is also the issue of a hole for the MPFI injector that would be a real bother for an SPFI engine to run.
You can, however, swap the heads out as the blocks are the same, and use the SPFI intake manifold. The SPFI computer will then run the engine as if it were SPFI--the only difference is in the heads.
THIS IS ASSUMING YOU HAVE A NON-TURBO MPFI MOTOR.
In order to put the MPFI motor into the SPFI car and run it as MPFI, though, then you have to rewire, put in a new ECU from an MPFI car, and maybe swap gas lines (due to volume per unit of time issues). There may have been another item if you were to keep the MPFI but it would only have been a minor thing if I did forget it.
So yeah, there is the info if anyone else has the same question some time. Thanks again guys, for pointing me to the right questions to present the dealer with, it saved a lot of time (and I also like getting the same answer from more than one source). And if anyone knows the tranny question, let me know! Otherwise I'll try to remember the next time I'm at the dealer with a knowledgeable tech.