Yep, Tim
We are all in agreement.
However, I wish Warren Foster (wdoftexas) was still around. He was a GM truck-parts expert (his career at GM gave him knowledge and authority).
If Greg Hill reads this maybe he will confirm/correct Warren finding a later date casting of a 261 block that seems to have traits of different-year 261s (presumably allowing them to be replacements in various year vehicles?) - same block casting code as the 1962/1963 261 block, and a later casting year.
Warren sold me a 261 that date codes later but has the water pump design of a 54 block. He said they were over the counter engines designed to be a drop in replacement for the 216s when they failed. I think the casting numbers matched the 54 design but the actual date code was later.
