I'll give the VIN decoding a shot using info in the 60-66 assembly manual.

For H3C519B:
H=heavy duty=24000 GVW
3=last digit of model year=63
C=conventional cab
51=series (5=1.5 ton)
9=body/chassis type=stakebed
B=assembly plant=Baltimore

The rest of the number is the build sequence.

American Classic's decoder only covers thru the 1-tons--no big bolts. There used to be a decoder on oldtrucks.com, but it seems to be perpetually offline.

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