I recall that the SBC double hump heads, casting numbers 3917291 and 3782461, do not have screw in studs. Those are probably the "double hump" heads you have.
I had a pair of 3917291 heads on my '56 Chevrolet. They had pressed-n studs and were pinned. They were ported and flow tested by the late Joe Mondello in 1970. Mondello told me that they were the best of the "double hump" heads.
Last edited by MouseFink; 01-31-2013 at 01:53 PM.