What old vehicle has 20"x4.5" or 5" steel wheels that I could possibly find to use for my next project? And on the cheap. Coker has them for lots $$$
Milk truck wheels or "high clearance" wheels. Be prepared for heart-stopping type of shock when seeing the prices. Edit: didn't read the "on the cheap" comment. Sorry, I've got nothing now.
If you wanted 18s or 21s I would say motorcycle wheels. But 20s are going to be a little odd. I would not use space savor spares for wheels on a rod, they are not intended for general highway use and don't have a lot of lateral strength.
On the cheap, is the Dodge spare like Rich said. Send them to weld craft wheels in Michigan. www.weldcraftwheels.com they can narrow them for you. You can usually find the wheels on the auction site I can't mention. they will have either round or oval holes that you can have blanks cut and weld them in. I hope that helps!