15x8 with a 4.5” backspace. With the SBP axles it’ll be tight to the springs, but you can use a small spacer (3-5mm) without any issues if you don’t like the spring clearance. You can run less backspace, but the next common size is usually 4” and that’ll put the tires right on the quarters. Your car doesn’t look to be raised much in the back, so it’s better to have a little more backspace and adjust with a spacer if necessary than not have enough. Just my opinion though. If you hang them out 70’s street freak style you’ll need new springs with a higher arch.
