440 heads

The early to mid 60's 516 and 915 were both closed chamber heads and gave you almost a full point in compression over the open chambered heads like the late 60's 906 and early 70's 452. They both however did originally come with a small exhaust valve 1.60 and most of the time were changed over to the large 1.74 (standard in the 906 and 452) exhaust valve, yes they are my favorites. As long as yours has the large valves you're good to go.