The size and location of the propane tank is somewhat optional. The type of tank is not. It must be a liquid-draw tank certified for vehicle use. Many people mount them on the framerail as shown here, but take care to locate them at least 19 inches from a major heat source, or behind a shield. Some use bed-mounted tanks, which is also OK. Special propane hoses are used, and all connections should be leak-tested prior to operating the vehicle. In addition, the hoses should be solidly secured every 24 inches.