Welcome aboard VMF
nice car dude.
Id bet you have a weak igntion. replace the coil, check the points, wires, cap and rotor and make sure you have 7-9 volts to the (+) of the coil with the motor running
1970 Mach 1 San Jose built Dec 23 1969. Marti says 1 of 7. Purchased in 1987. Original family owner of the powertrain 351C 2v FMX.
1993 GT 11,000 miles, Built 2-12-93 Auto, 3:27 Axle, cloth, sunroof. Untouched except for rubber and battery, Purchased new 8-3-93. still has the factory windshield fluid and new car smell.