All 3 sets are basically the same casting and have the same combustion chamber and exhaust port size . The 502 and 344 heads were bridged rocker heads, the 090 heads had individual rockers. My choice is the 090 heads. You can use small block Chevy rocker studs and AMC roller rockers without any extra machining or guide plates.
Look closely at the pushrod holes. The 090 are oval, the 502 and 344 are round. The hole in the 090 acts as a guide plate.
http://www.bulltear.com/forums/showthread.php?9483-idea-Head-information-%28casting-numbers%29
Bob
tufcj
