Ballast resistor-> 4 prong to 2 prong

I've always had luck with GM HEI. Cheap and only 4 pins w/ ground. Most important thing is to use a quality 12v coil and to bolt a heat sink with transfer compound to the unit, or bolt it to the fender away from headers. HEI is cheap and compact, and if you're interested, the 5 pin unit has a built in spark retard of 10 degrees by grounding the 5th pin. Good for hot restarts, high compression small blocks, or pinging up a hill on hot days, bad fuel, etc.