F56Y is a '56 passenger car 235 (140 HP rated) manufactured in Flint, MI, originally mated to a Powerglide (would have had hydraulic lifters).
F1208AE (an I was often used to stamp a one), would be a '58 (or later) passenger car 235, manufactured in Flint, on December 8th (year would need to be determined from the date code near the starter), originally with HD clutch. This info is from my '58 Chevy Master Parts catalog, and if the block date code is after '58, the AE suffix would need to be double-checked.
Tim decoded the F255X - '55 second series truck, 235 (120 HP rated, would have solid valve lifters, if still original).
JAD is a '51 (RPO 317) 235 (105 HP rated), passenger car service, manufactured in the Flint plant, and as Frank suspected, it would have been mated to a Powerglide, and had hydraulic lifters. It also is a "low pressure" splash/spray oiled, Babbitt rod bearing engine. This info is from the '51 Chevy car VIK from the GM Heritage Center site archives. All of the other engines are all "full pressure" engines with pressure-oiled insert rod bearings, and perhaps preferable, by comparison.
F54Z is a 235 (115 HP rated) manufactured in Flint, from a '54 passenger car with standard transmission (as indicated by the Z suffix). In '54, cars with standard transmissions came with solid lifters, and the block is not factory drilled for the oil gallery needed to support hydraulic lifters. Only 235s in Powerglide equipped cars in '50-'55 came with hydraulic lifters, and had the corresponding gallery drilled at the factory ('55 was the transition year, so '55 blocks need to be double checked, drilled or not drilled) . I'm running an F54Z engine in my '53, and it is a sweet running engine.
Jumping out of order, the F56Z is a '56 passenger car 235 (140 HP rated), which follows the same decoding pattern as the F54Z, and except that it would have come with hydraulic lifters, regardless the transmission type originally fitted.
F302JC (assuming it's a Chevy engine, not a GMC as Frank suggested), is a '58 or later 235 Thriftmaster truck engine from a 4000 series, with HD clutch. If the block date code is later than '58, the JC suffix should be double checked for model application. Info again from the '58 Chevy Master parts catalog. 302 would indicate a March 2nd manufacturing date.
FWIW, the '54 engine might be the most straight forward swap into your '53 (water pump is the same older style), but engine condition should dictate which may be better.
Good luck!
Doug
Last edited by drdoug; 01/04/2021 2:01 AM.
