Iv been looking into the MSD tach deal.. But the one summit shows with that part number has alot less wires than the 6 shown in the diagram. Also.. I was told I have a tach made for a mag (guessing that means an AC tach) Think the MSD would work still? Says transfers the Mag to DC volts. Heres a link to what Im looking at. http://www.summitracing.com/parts/MSD-8132/
Check online for the manual for your make/model of tach. Might involve a few emails or phone calls to verify, but Could well be, in which case you're set and don't need that adaptor. Would be unusual to just HAPPEN to have such a tach.
The current MSD unit is different, but works the same. Call Joe Hunt with what you have, model numbers, etc. 916-635-5387. I'm sure they can tell you for sure if you can or can't, or what you need to do with what you got.

This should be the same info for anyone using the Vertex style internal transformer magneto. They are all the same mag, beleive it or not. The Mallory and MSD mag's are pretty much the same as well, but they are external transformer units also from the same Vertex, but external design, making them much easier to adapt to modern electronics. But I have a soft spot in my heart for the purist internal units.....they're Soooooo badass!
Ray