What stangs came with the 351's

[PKRWUD]

On that engine, the 1970 heads worked better. The valves in the '69 heads were too big. That's why they reduced their sizes for 1970.

All 351C 2V heads were open chamber, but the '70 & '71 4V heads were closed chamber. They called them "quench chamber" heads, but they are closed chamber. Try and find some pictures in your reference material, and you'll see what I mean. The Boss heads and the 4V heads have identical combustion chambers.

Take care,
-Chris

P.S. If you really want to throw a monkey wrench into the works, consider this: The 351C (casting numbers D0AE-J & DOAE-G) was installed at the factory in a few 1969 Fords.