Wheel backspacing

I had 15X10 jegs sport lites with 4.5 back spacing and BF Goodrich 275/60/15 on my 73 Dart Sport If i hit a bump hard enough it would rub on the wheel well if I had 4.75 back spacing would have been perfect. Maybe buy the 10" with 5" BS and run a 1/4" spacer or 3/8" spacer if needed. I did have superstock springs on my car for what its worth.