I chose to use the gas tank (new) for an '87 truck. One of the dilemma's being that the '80 truck tank has a different size hose nipple (smaller) than the '87. After having searched the "net", 'cause that's what everybody says to do, I found various ways to adapt the early/late fuel fill arrangement, like; take the tank to a radiator shop and have them solder a smaller nipple onto the new tank, or; use an exhaust pipe reducer to join the old hose with the new tank. After going blind from all the search, all I could think of was the commercial that said "The internet never lies....bonjour"
Well, I pulled my tank to see exactly what I was up against, and immediately I thought WTF is everyone thinking? Yeah, the tank end of the hose is smaller, BUT!! The filler pipe is the SAME size as the new tank inlet! I just got a fuel hose from Gates that has a 90* bend (all of $17) cut it at where I marked with the green tape (see pics) and hooked everything back together. As simple as that
Later...
Lee