opinions needed regarding available EFI for a small block

Multi-Port Injection (MPI) should give much better fuel distribution than any single-point Throttle Body Injection (TBI). I have used the old Holley Pro-jection on a Mopar 383, but always quirky, even with O2 feedback. I understand their last Pro-jection model finally added enough sensors to make it work OK. The Holley Commander 950 replaced it and works much better, w/ versions for TBI and MPI. Usually the TBI version brings ~$650 used on ebay.

FAST, Motorvation, and others are TBI, but use 4 (or more) MPI injectors. That makes it easier to change injectors for tuning and probably gives better distribution than older TBI. Some may have a common source since they look similar. The cheapest TBI would probably be the Mopar factory system used on the last SB trucks before the Magnum (~1985, check www.AllPar.com). I saw one on a JY Dodge truck recently, but wouldn't want the cast iron intake. Your engine should run fine with that ECU if the same displacement. I don't think it needs any signals from the block or heads (ex. crank sensor), but verify.

For MPI, using the factory barrel-keg intake would be cheapest. However, for a direct mount, you must install Magnum heads. Many people prefer those anyway. You also must verify hood clearance. I hope to adapt one to my 273 heads eventually. I don't think you can use the factory ECU without a crank and a cam sensor. They didn't use the cam sensor for spark since still a mechanical distributor. Many after-market ECU's can control MPI, such as Megasquirt or Commander 950. The only other MPI intake I know of is an after-market low-rise for Magnum heads. If you use the beer-keg, it needs a stiffer plenum plate and maybe cut back the runners for better top end (search ebay).

Megasquirt is a high threshold, with much custom wiring and electronics knowledge. It also isn't cheap, usually $250+ for a used newer ECU, and even the latest is a bit dated design with kludgy add-ons required for MPI and COP ignition. I read a lot that are "works in progress" and many people giving up and selling out. I am sure some are daily drivers, but haven't heard of any on FABO. While I have the background to do Megasquirt, I decided not. I got a used Commander 950 ECU on ebay for $120 that appears easier though still need to make a harness. I will leverage a Magnum harness I have.