I'm putting some new wheels on my '83 Cutlass. They're the correct bolt pattern, but I'm not sure if they've got the correct backspacing. The came off of a '70s Lemans/GTO. They rub the rear frame rails barely. They fit the front just fine, but the dust cap prevents me from putting the centerpiece on. The tires and wheels measure 29.3" tall and 10.4" wide. I'm contemplating switching to another tire that would be 28.1" tall and 10" wide. Would that solve my frame rail rubbing issue? And what can I do for the dust cap issue? Is there a flat dust cap or something I can use?