Yes, Mach 1's would be different. Like Joe stated, '70 Shelbys were holdovers from '69. Mach 1's were not, and have dates specific to their year/month of manufacture. As far as the C scratch goes, that's just a bragging right that nobody will see, and will have to take his word on. I understand wanting a car to be as near perfect as a person wants to make it, but sometimes there has to be concessions, and this one wouldn't matter. Finding date code specific 428 blocks is no easy task. My friend just went through this last year to find one for a '69 Q-code GT that I sold him. It took him over a year of INTENSE searching, and 2 blocks, to find one that was usable.