Further fodder,
All 1941 to '48 Chevy sixes used 10 mm spark plugs: the really tiny ones!
Have had two '41 to '46 big Chevys w/ the Liberty 235.
What can also confound things is that the 1954 "high-pressure" 235 will pretty much bolt-into Chevy cars & trucks back to 1941, so there's also retrofitting going on, so someone might speak of the "235 in his '41".
