That casting number has almost always been described in all the various lists as 56-62 which suggests to me, right or wrong, that the block was a service replacement block. You can see it has the 55-57 motor mount boss and the later side boss. Thus, if you were using it on a 55-58, you installed the original head and rockers, and used the plug and drilled bolt. If you were using it on a 59-62, you just installed the head and rockers and you were good to go. The question is, and I don’t know the answer, is whether gm was still casting service replacement blocks as late as 66. So possibly the casting date is 66, I don’t know.
I know with respect to passenger car rear ends, gm was still casting service replacement centers and posi units as late as 1969 so it’s entielry possible they were still making up replacement blocks. Remember, the last 235 was installed in 63 in a pick up with 4x4. So 66 was only threes years after. So it’s possible. The later rockers, could have been the installer did not read the directions correctly and installed the bolt and plug into a block that did not need them.
Last edited by Dragsix; 04/09/2020 1:34 PM.
