4" Backspacing is ideal on an 8" wheel on one of our cars. Unfortunately, you're not likely to find this on most off-the-shelf wheels. If you're getting some custom wheels, it's easy, but with most companies, you'll either have to get a 3.5" or a 4.5". The 3.5" will work...I've run that in the past. I prefer a 4.5" BS, but I typically install the thicker aluminum brake drums along with a 3/8" spacer to center the wheel. HTH