Charley - This is the same engine we have discussed before in your
08/07/2023 Engine Shop thread.
We had pretty much confirmed the engine is a Canadian 261, but didn't have a couple of the newer picture you posted above. The picture of the block casting number with the "M" inside the square outline confirms it's a Canadian engine manufactured by McKinnon Industries as shown in the reply above from Kevinski.
You also posted a new pick with the block casting date code "1 K 26". If I'm decoding that correctly, that makes this a 1961 engine built October 26th.
The more I look at all the pictures in both posts I think it's from a Canadian big truck Chevy. The pinched off larger vacuum tube on the intake manifold vacuum port that also attaches to the PCV valve setup (would have been original equipment) appears to be what would be present for a big truck hydrovac unit.
It sounds like it runs pretty good.
