ignition problems

Hard to read with few sentences, paragraphs, or capitals, which is probably why most didn't even try.

You say it is a Magnum crate engine in a 1991 RAM, so I assume you have the "barrel keg" intake w/ multi-port injectors. You confuse me when you mention a "carburetated (sp) fuel injection and computer" (what is that?) which is now "gone", yet you still have an ECU.

If you do have the "barrel keg", a common problem is that the sheet metal cover on the under-side pops a leak. This causes it to suck air, plus oil, so it runs lean and the spark plugs foul. It sounds to me more like a lean problem than ignition. A guy on ebay sells a thicker aluminum plate (~$100) that holds much better than the factory cover and solves the problem. He even has an improved design (~$150) with a deflector V for better air flow, if you also cut back the air runners. It would also be very stiff. For either, you must remove the intake, which is a bit of a hassle in a SB since you have to drain the coolant, etc. BB intakes are easy to swap.