I would like to know if the fuel tank for a 1991 super cab is the same as other years

 

Rangers had 2 different gas tanks, 16.5gal and 19.5gal
Extra cabs got the 19.5gal

Ford switched to plastic tanks in the late 1980s, early 1990s, you usually have to repair these, as replacements are hard to come by
Plastic welding is used for repair, that's how these tanks are made, 2 halves plastic welded together

Fork lifts in wrecking yards often damage them AND wrecking yards drill holes in the bottom to drain all the fuel before they are put out into the yard, environmental thing