Gonna be honest with you, tried both. HEI (as in externally mounting the module), never did get it to hit and I couldn't figure it out. Then went 4 pin Chrysler with a 4 prong ballast and it sparked well but somewhere along the line that blue coil + wire on the factory harness sparked something (unplugged and wasn't taped), and I blew a fusible link. After that I never could get the 4 pin box to work, had an old mechanical 6al box laying around, hooked that up and it ran like a top, and still does.
I'm not sure if that blue coil + wire can be used on the Chrysler setup, but the way I had the ballast setup the starter would stick when I tried to use it for a keyed hot going to the ballast, ended up using a power wire in the lean burn harness by the battery that had power when keyed on and when cranking, for the MSD.
