I'm confused. Isn't the only thing different between the Mach 1 and standard gauge set up, the wood grain simulation that surrounds the bezels? If there isn't a tach, then the gauge set up is the same (except for the little horse that I believe lights up when the High beams are on). And if I am correct, and you don't have the sport lamp switch in the dash. you can easily supply power to your grille lights by tapping them into the parking light circuit.

I have my Mach 1 dash gauge set up, and I have a gauge set up from a standard 70 Mustang, and the gauges are all the same.