Need some help controlling body roll

The car originally had the dog dish hubcaps with steel wheels. When they sent me a video of the car it had rally type wheels on it. The dealer had no idea of the history of the car so I am left to figure it out. I just want the cheapest option to fix it. I figure leaf springs will cost as much as rally wheels with the proper back spacing. The springs still may be bad. Somebody put black undercoating on without removing but the drivetain and the exhaust. I might as well try and get the proper wheels for the rear. I don't want to cut the metal. A sway bar may start off as the cheaper option, but could easily start costing more in the long run. Time for me to hunt for the proper size rally wheels and figure out what siz is on the car.