Can not comment on whether it will suite your purposes, but TB 9-639 titled "Passenger-Carrying Capacity of Tactical and Adminstrative Vehicles Commonly Used to Transport Personal" gives these numbers:
2 1/2 Ton Cargo Truck - 14
2 1/2 Ton Extended Cargo Body Trucks - 18
2 1/2 Ton Dump Trucks - 10
5 Ton Cargo Trucks - 16
5 Ton Extended Cargo Body Trucks - 20
5 Ton Dump Trucks - 12
5/4 Ton HMMWV Troop Carrier - 8
5/4 Ton HMMWV Cargo/Troop Carrier - 4
5/4 Ton M880, M881, M882 - 8
Semitrailer Personnel Van - 80
It refers the reader to AR 385-55 or the operators manual for vehicles not listed.
I will try to attach a snapshot of TB 9-639 to this post.