yes you can run MSnS without the relay board, just gotta wire it differently and you'l have to wire the relays individualy, my problems with the HEI? well the things gets crazy hot and burt my fingers, I've burnt 2 of them up, finally got a flamethrower HEI and it's lasted quite a while, and the revs kind of fall off at high rpm's getting it to rev over 5500 is about impossible now, I'm running a MSD blaster 2 coil, yes you can run the Z31 or gm coil, they are rpetty universal, they are not all equal but they are pretty well interchangable