If that's the way you want to go, look at grafting a 1988 and newer Chevy tank in there. I just replaced the tank in my 89, it's just a couple of brackets, a couple of straps and the tank. You have to remove the electric fuel pump and extend the pick-up tube to the bottom of the tank but it seems rather doable to me. You will have to graft a filler access into the side of your quarter panel regardless of which tank you use,
Scott