Here is a link to pics of my 261, showing a block casting date of D3 3, or April 3, 1963. I pulled this engine from a '55 school bus. Note the mismatch between the head and block casting dates. There is no number stamped on the pad next to the distributor.
Joe D.
most likely, that's a replacement block, rather than one from a different truck. GM did produce the 235 and 261 engine blocks well into the '70s, both for domestic replacements as well as export use. It's my understanding that they were casting the blocks at a plant in Arizona, but I have no evidence to back that up. Just what I had heard.
