If the code cannot be found, then identification can also be made by looking at the case measurement from front to back, not including the bell housing or rear pump section.
SMALL CASE = 9 7/8" Case Length (1951-1970)
IP - 1951-1954 Ford, Mercury 215, 223, 239, 255
PAD - 1953-1954 F100 215, 223, 239
PAE - 1954 Mercury 256
PAG - 1955 Ford 223
PAH - 1955 F100 223, 239
PAJ - 1955 F250, F350 223,239
PAK - 1955 Ford 272
PAP - 1956 Ford 223
PAR - 1956 Ford 272, 292, 312
PAS - 1956 F100 223
PAT - 1956 F100 272
PAU - 1956-1962 F250, F350, P350, P500 223
PAV - 1956-1958 F250, F350, P400, P500 272
PAY - 1957-1962 Ford 223
PAZ - 1957-1960 Ford, Edsel 272, 292, 312, 332
PBC - 1957-1962 F100, F250 223
PBD - 1957-1958 F100, F250 272
PBM - 1958-1961 Ford, Mercury 312, 332, 352
PBW - 1958-1962 F100, F250 292
PBY - 1958-1962 F350, P350, P500 292
PCC - 1961-1962 Ford, Mercury 292
PCD - 1961-1962 Ford, Mercury 352
PCT - 1963-1966 Ford, Mercury 260, 289
PMA - F250, P350 215, 223, 239