14000 lb is normal rating for a 4100 1.5 ton AD truck. I think brake booster was optional on the 1.5 ton, but not sure.
Do you have a bracket on the frame under the cab right side rear where the booster would have been? Do you have big vacuum lines on the firewall and under the cab? Have the brake lines been messed with and rerouted as if a booster was there?
Just some clues to look for to answer your own question.
Grigg
