IINM, The war trucks were serialed as a 42.

So it should look something like this:

00BP-M00000

00 - Plant Number
BP - 1942 Half Ton
M - Month Code
00000 - Serial Number (series started at 1001)

~#~#~#~#~
1946 Chevrolet 3600 - "Old Number Seven"

Cavalry's Here. Cavalry's a frightened guy with a rock, but it's here.