Depends on the year of the head and block. There was more to it then just the bolt, there was a plug also. In 59, gm changed the oiling system slightly from the 55-58 motors. Service replacement blocks for 55-58 motors eventually changed over to 59-62. So if you had a bad block on a 55-58, the service replacement was the 59-62 type. In order to use the later block with the earlier head and rockers, you installed a tapered plug and the drilled bolt. Was not needed if replacing a late block with a late block, and using the later head.
So you want to see what year block and head you have on your hands there.
