(some 78) plus 79 and 80 are only exact fit. 81-87 will work if you swap or modify the crossmember on the frame. Last year I played He11 finding one for my son's 80. It had come to him with a cracked original tank, jerry rig patched good enough for past owner to sell. I found one in a blink and miss it kind of junkyard about an hour from home. came out of a 79 long bed my son's is an 80 shortbed (and my kid's is a stepside besides) Went right in. the earlier 70s with the same body style are different, dont know how they'd mount into a 79-80 but the filler neck is much different, wraps around to the inside of the tank (towards the middle of the truck) MIGHT work if you get the filler neck and hose that goes between it and the tank, never tried that swap.