F = Flint, Michigan truck engine assembly plant (where the engine was assembled)
I think the engine blocks and heads were cast in a separate GM foundry/casting plant. Maybe someone knows for sure?
The reason that I asked about the location(s) of the two codes is that it is common for someone to have a replacement engine. A replacement engine might have a variety of codes pressed/stamped into the block, usually because the title/registration might be the old/original engine serial number (a poor choice because engines were often changed).
People have reported a variety of styles of codes in replacement engines. I have one 1954 block where the code has be roughly ground off - it has no engine serial number.
The codes you posted are:
- the block date casting code (cast as part of the block)
- the engine serial number (pressed/stamped into the block)
Here are locations of various codes on 235/261 blocks/heads The codes that are sometimes of interest when identifying an engine are:
- block casting code
- block date casting code
- head casting code
- head date casting code
- Engine Serial Number
