Pilot,

I am almost certain that I have an AC S-6 oil filter canister. After considerable hunting, I found the following numbers:

NAPA 1100

AC P115/127 LEE L51
DELUXE WD37
FRAM C21/C21P/CH105PL
HASTINGS LF101/207
MOPAR 921178
MOTORCRAFT FL333
PUROLATOR P51/P125 (now L20051 ?)
WILLYS 119952
G.M.C. 5572288
TEXACO T5

WIX FILTER # WX51121 might be the same.

Note that there are a wide variety of Fram and AC (and other) canister style filters that varied in size over the years. Quite often a canister-year does not match the truck-year. The S-6 was sold from 1955-1962 Chevy 6s and on the 1955-only Chevy V-8. Also, the canister from other-year and other nameplate GM engines might have been installed on a truck engine.

Fram C31/C31PL/C4/C4P is for an earlier AC canister (S-2 ?)
Also, Purolator L30034 might fit an earlier canister.

Your best bet is to obtain as many numbers as possible and then take your canister to the parts supplier. I had to go to several different stores before I was able to match mine.

Tim