Mopar OEM EFI
Personally, I'd blow off the factory system for a Megasquirt set-up. That's what I plan to do with my truck someday. There's a member here who works for a company that makes a kit utilizing the megasquirt system, I think it's Madscientistmatt and I'm sure he could give you a wealth of information.
That would be me. Right now getting it to work with the factory distributor is a bit experimental but there's 1 or 2 examples running around. Earlier Lean Burn distributors are a cakewalk to deal with though. I have one on my slant six MegaSquirt powered Dart.
As for what other systems can work with the factory distributor (some of the less expensive ones will require substituting a dual sync) - I know Haltech will, I think BigStuff3 might, I know the Holley, Accel, and FAST systems won't. Not sure on Edelbrock's - it's based on the very high end EFI Technologies system, but they may have locked you out of a lot of its features to simplify things. The factory EFI has an eight tooth crank wheel and a one tooth wheel in the distributor.
If you're going with an OEM ECU: An OBD-I ECU might be easier to swap over, but there's
no tuning options. SuperChips makes tuners for OBD-II, but you have to swap over more sensors. Often, tuning factory EFI beyond some basic adjustments has a pretty steep learning curve compared to standalones. It depends on whether you want to get it up and running, and leave it close to stock (an OEM PCM would do that just fine) or want a modified and tuned engine. I'd probably use a manual transmission PCM - that way it won't care about the trans. The ignition is completely built into the PCM except for the coil and sensors; there's no external ignition module.
More notes - I believe the PCM just controls the tach and no other gauges, and can probably drive most aftermarket tachs. They are all speed density; Mopar hasn't been a big fan of mass air flow sensors.