zurgrow
i'm using an msd-2 coil, as a stock replacement, with an aftermarket tach. and had no issues.
there was some talk at the parts store about how it may affect the tach, but i didn't understand the concern. the tach is just a pulse counter(i think) and senses the pulse at the negative(-) terminal on the coil.
i have a chilton manual and it's only marginally helpful.
somebody on here must be using the msd-6 and have better info for you.
richard