Geicoman and Allen perfectly described the differences. Think of Mach 1 being similar to a GT package. It’s just an upgrade from a regular sportsroof. I would do what Geicoman recommended and get the Marti report. Congrats on the car and welcome to VMF. You won’t find a better forum for exchanging ideas in regards to early model mustangs. Also post some pics!
67 Fastback S Code, Brittany Blue
Work in progress