You have to make sure your engine has
oil galleries in the lifter area, as some 427 SO's were solid lifter only, and with these engine blocks, you can't run any type of hydraulic cam. if it is a hydraulic lifter block, it should have
oil gallery plugs in the back of the block on each side of the cam plug.
if your block is truly a 1965, I would guess it is a solid lifter block.