I have a 351 in an 83 mustang. I'm running trick flow heads now but was running early 351 heads before (1970 casting) Early 351 heads have slightly bigger intake ports and valves. I think in 77 or 78 351 heads and 302 heads were the same small ports and valves except 1/2" bolt holes for the 351 and 7/16 for 302.