According to my How to Rebuild your Big-Block Ford book, they are a 68 std. head for a 360, 390 or 428 w/air tubes. My guess would be it is a 390. Check to see what exhaust manifold bolt holes you have. The GT and some 69 Mach 1's used those heads and they should have a 14 bolt pattern for the exhaust. Also there should be threaded holes in the heads for the smog tubes. Although my 390 Mach 1 has those same heads and there are no smog tube holes. The 69 390 did not have smog on them, except maybe in California.