Awesome, I ordered 15x8 wheels with 3.5 backspace so that is good to hear. Are your leafs in Stock location? Mine are, that's why I went with the 3.5 bs.
Everything is stock location Pro Sport. Pic below is with old leaf springs on it and I had 15 x 8 cop wheels with 255/60/15 M/T drag radials. Car sat lower and they sit easily. I actually had 10mm spacers in there as well..