I did some searching here and a few other sites and haven't found my exact answer so here it goes. Ok with income tax coming im putting some money away to find some used rims prob on Craigslist or threw a friend. I want to get some 20s and still lay out. I know the bolt pattern is 5x4.75 or 5x120.65. but im unsure on a few thing as for what off set I need and back spacing. how do I determine what the offset and backspace is on a used set of wheels? will most universal 5 lug fit? is there a way to messure the wheels with out trying to bolt them to the truck. what size tires should I run? and will I need to tub the fire wall? what width should I get 8.5 or 9?