late '65 140hp with the improved carb linkage also had all 3/8" shroud bolts....also I have in my stash of parts a '64 110 head, part # 3886256, that has all 3/8" shroud bolts, does any know why GM would have produced a '64 head with all 3/8" bolts and then reverted back to the mix of 1/4-20 and 3/8"???? O. B. Stewart Music city corvair club