1956 - 1959 ("Task Force" trucks)
The first and second symbols indicated the Series (all light trucks had a "3" in the first position). Third and fourth symbols indicated the two-digit year. The fifth symbol indicated the assembly plant (now changed to letters from numbers). Last was the the sequence number (6 digits and started with 001001 at each plant).
A "6B" suggests a 6400 with a 156.5" wheelbase.. the "A" would seem to suggest it was assembled in ATlanta, GA.
