Studebaker never built a 6x6 tractor but built a 6x4 model. Semi-tractor/trailers have limited off-road performance, and are not rated for full off-road use. The M35 and M211 series fifth wheel load rating was on road and off-road. A trailer could be towed on road and a trailer off-road. All series had fuel and/or water tank versions on long wheelbases. Capacities were to in 2 or 3 compartments, depending on the series and whether carrying gasoline, water, or other liquid. Most had pumps and some had heaters. Most World War II could be fitted with bows and a tarpaulin to camouflage themselves as common cargo trucks. The CCKW, M35, and M135 had a van model on a long wheelbase. These could be equipped for many different roles. The M35 also had a model with slide out sections on both sides. Van bodies were used for medical, communication, machine, repair, and other shops. They could have different sizes, window arrangements, and other special equipment. "Expansible" vans are used for communication equipment. The GMC CCKW and M35 series had chassis-cabs in different wheelbases for specialty bodies. Maintenance, engineer, water purification, pole-setting, air compressors, fire fighting, and other equipment were also mounted on chassis cabs.