Yes Ed, the MAC works with my C&L 76mm MAF. I don't know of anyone else who makes Mustang MAF units that are 73 and 76mm, probably patented by C&L/Vortech.
Regarding the headers, aren't those the n/a 3.8L T-Bird tubular manifolds I was considering once upon a time? If so, I checked them out at a local wreckers, and the stock units are MUCH bigger in diameter and volume potential than those things, IMHO.
Anyway, they looked like the flange position was the same as the stock SCs, but I could be wrong. I certainly wouldn't bother, Les, if you have to start muckign around with those. They are stainless steel though, not cast iron, so no porting can be done to them.
What are the MAC headers made of?