should be a vin plate on the drivers side of the dashboard, viewable thru the windshield.
If the drivers door is the original, there should be a plate riveted into the door that will have the vin as well as option codes for the color, trans, etc.
Also check the core support, they may have used a buck tag that would have the vin on it, but Ford eventually stopped using them sometime in the 1970s.
'72 Mach 1 looking for info
