Thanks Bluebird428! Interesting discussion there. My garage thinks some shade tree mechanic did it back in the day for some reason (he probably thought it was good), but it is really causing me a headache. As far as the heads go, all I have to go on is what the garage researched. They thought the numbers were consistent with the rest of the motor. Thanks for the tip on the locking nuts, luckily the rocker arms that I bought (that we thought would slip right on) have the locking nuts on them. It's been an eternity since I dropped the it off, just hoping they can find something off the shelf from Butler.