flat head motor id

[oldsman41]

i know google is my friend also the archives but still have a problem iding this flatty. engine has the cast bell housing but the fuel pump rod is the 10 ich long one which is for a 49 -53 right? i thought 48 was last year for the cast bell housing. no markings on the housing just on right rear of block is something than L 431 has eab heads on it. can someone help here? thanks