HEI and OEM ignition interchange-plug gap scenario

No problem. Even a points ignition can throw a spark across a 0.250" gap at 1 atm pressure. Thus you can at least idle. As you go WOT, you will reach a cylinder pressure where the spark can't jump the gap. I had that problem in my 1996 2.4L, it would start missing trying to accelerate on an on ramp. I followed the Chrysler TSB for 2.4L turbos to reduce the gap (0.060 to 0.050" or such) and no more problems. Mine isn't turbo, but perhaps the accident that shoved the engine controller made cracks on the circuit board, or maybe wires start leaking as they age (changed plug wires, coil pack, ... no help).