1954Chevy5Window,

It looks like a later 261 (1/2" NPT holes for oil lines) but I do not see the full-flow oil filter "selector plug". Maybe the "plug" was not used if the full-flow canister was installed at the factory? (I'll check my 1960 261)

Here are locations for various ID codes:
Find and port:
- Engine Serial Number-
- block casting code
- block date casting code