the 3 part indicates the "light" truck group, the 3xxx models
3A = 1/2T, short, 3100
3B = 1/2T, long, 3200
3E = 3/4T, 3600
3G = 1T, 3800
for lots of detail about models and factory options [called "RPO"s] get yerself an assembly manual ... for dealer available/installed options, there's accessory manuals, the 57 one below has most of what would have been available for your year, but doesn't include the RPOs
Bill
