Factory EFI A body conversion

Forget about OBD1 Dodge PCMs unless running a basically stock engine. The OBD1 PCM will have one single large harness connector plugged into it.
The OBD2 systems can be easily tuned, are more plentiful in wrecking yards and used trucks, and just as easy to wire in. The OBD2 system will have three small harness connectors plugged into it.
The biggest issue you'll want to consider is the factory systems use the flex plate for crank sensor trigger wheel, and they are the weakest link. With mostly street driving they are usually fine, but if you plan to hook up on slicks a lot at the dragstrip you may beat up that factory flex plate. Not sure if anyone makes a stronger flexplate that includes the crank sensor reluctor windows.
What's the intended use? Which intake bolt pattern do you have, LA or Magnum? Do you want; a dual plane, single plane, or custom intake?