the tank will be 16-18 gallons like all GM trucks back then - measuring it out: inchesX inchesX inches / 231 = gallons .... or about 7.5 US gallons/cubic foot
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics