313300F54XA is the engine serial number, and it decodes as follows:

313300=build sequence #
F=Flint engine plant
54=model year
XA=regular production "Thriftmaster" 235 used in the 3600 series (3/4-ton) trucks.

That other number might be something the state stuck on the pink slip. It doesn't look like any type of Chevy number. 54PU probably stands for 1954 pick-up. No idea about the ZB.

Curt
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1953 Chevy 6400, 1957 Chevy 2dr Sedan
--"Mediocrity is easy, the good things take time"