15x10?

On my 70 Dart, I had A narrowed Dana 60 built to 49 5/8" disc to disc, I did a mini tub job and spring relocation and I have two sets of wheels: 17x11 with 4 1/4" backspace with 315/35/17 tires. The second set of wheels are 15x10 with 3 3/4" backspace with 295/50/15 tires...