I don't know the condition of most of these expansion tanks, all I know the one out of my 87GT is toast. So I decided to make one. I made it out of .040" (1mm) material and folded the sides to make the tank. Here's the new tank next to the old one.
Notice the rust and holes in the original tank. One of the previous owners screwed something to the wall where the battery used to be and drilled three holes right thru the exp tank.
Two steel lines are welded in, one at the bottom for fuel return and one at the top for fuel expansioin.
This pic shows the bottom tube welded close to the corner which is the lowest point.
This pic shows the tank in place with tabs welded on for securing the tank. (Not painted yet)
I have about $20 invested including the brake line to make the return lines. I don't know if these tanks are still available and their costs, but I'm lucky to be able to fabricate just about anything I set my mind to. Hope this can help you make your own.