Hi,
The Clevland engine has large oval port canted valve heads. They used this for the '69 Boss 302 mustang. The heads made good power at high rpm's, but were useless on the street as they had no bottom end power. It's hard to find an old boss 302 as most were blown up trying to rev too high. I would stick with a Windsor small block as the new heads make more power than the old canted valve heads. If you really want 'race only' heads , the Yates heads are a modern version of the clevland heads and most Nascar Ford engines use them for 9,000 rpm power.
Perry.
