My recently acquired 1970 Sportwagon that was converted to propane use is about to go back to gasoline. The tank has been unused for many years and has some funky varnishy stuff inside. It is not rusted out, just nasty looking inside. What is the best cleaner/conditioner/solvent to clean it out? I don't want to use a sealer kit as I have heard as many problems with peeling and flaking sealer and how clean you have to get them for the kit to work properly. Or is there a new tank option maybe? I looked online and the part number they list as a Sportwagon tank is also the tank for B-Body fullsized wagons. Can that be? Does anyone know their tanks? Thank you in advance.