74 Duster stock springs, stock 8-1/4 rear

15x8 with a 4.5" backspace and 275/60/15's should fit with the 8.25" rear axle. Obviously you should measure your car, the spring to wheel mounting surface and wms to quarters is what you want to look at. But on a duster you should have the room. If you had an 8 3/4 I'd say get some more backspace, but the 8.25's are narrower so 4.5" should be right.