I have a 90 3.9 (pre magnum?) in my 48 Plymouth coupe that is using the 90 OBD1 throttle body intake and EFI.

That 3.9 has some "health" issues", a Magnum 3.9 (92 & newer) is pretty easy to find.

I would like to keep the OBD1 because its there and functions, and I really don't want to have to rewire the car. Can I swap the beer barrel intake from the 92 motor with the 90 throttle body intake? What else may cause a problem?

While I'm asking dumb questions, is there an internal difference between a manual trans 3.9 and an auto trans 3.9, like a different center thrush main bearing?