The most common carbureted head casting numbers are: C8VE-A, C9VE-E, D0VE-A, D0VE-C, and D3VE-A2A.

All the above heads have 2.08 intake valves and 1.65 exhaust valves.

C8VE-A, C9VE-E, D0VE-A, & D0VE-C all have identical architechure, are completely interchangable and have 75-77cc combustion chambers. These are the most popular factory heads for performance applications.

D3VE-A2A's have a 96cc combustion chamber and a different valve train assembly that is not interchangable between it and the other heads. They can be made to work well but require more prepping.

Ther is also the D0OE-R Cobra jet heads (nice but rare) and the D2VE-AA heads (JUNK).

The heads and valve trains are all swappable between the blocks.

There is no such thing as 2-bbl and 4-bbl heads...they are the same thing.

I have a set of D3VE heads on my boat and the motor makes over 550HP.

Paul