1965/1966 Fastbacks, Convertibles.....289 HIPO engine...K code...GT's
1969/1970 Mach1's....69's had 351 Windsors, 1970 had Windsors and 351 Clevelands and the 428's for both years.
Ideally try an find a 70 Mach with a 4 Barrel 351 Cleveland...some had Ram Air...
Mine is a 69 428SCJ...with a modified suspension/ 4 wheel discs and a lot of money in the engine to make it go fassst.
If U need parts and advice on a early Mustang....Ford....Bill Thomas is the guy to talk to...he's the Schmidt of Mustangs.