Since you don't care about keeping it factory, I say go HEI. You already have an e-distributor. I did that in my 64 Valiant slant. I actuate a relay (in a 95-99 Jeep relay/fuse box) by IGN1+IGN2 and run "12 V IGN out" to a terminal block on the passenger inner fender beside the HEI module. Get an 8-pin HEI module from a 85-95 GM V-8 truck (car to 93). It is inside their "small cap" distributor. Also take the GM "external coil" and the cable that connects it to the HEI module (plug & play). Snip the input wires (red +12V, wht tach) as long as you can and the distributor pickup connector & wire. Cost me ~$15 at PickNPull. Or buy same parts from TrailBeast here for $150. I also took the knock sensor & module from the GM (for use w/ Holley Commander 950). The 8-pin module is better wiring and will allow spark timing control down the road. Read on megasquirt site for more info. Don't use your yellow "crank" wire to actuate the relay. To answer your earlier question, coil+ should run 8-10 V (I think) when using the ballast resistor & Mopar ECU. All new ECU's don't need or use the 5 ohm resistor (electronics has improved since 1970's). If a replacement ECU has a 5th pin, it is usually a dummy (so dummy customers don't fuss).