you can go as much a 4.5 backspace i believe with stock suspension and still have room...
djvcuda's car is running a 17x7 with 4 1/4 backspace and when we measured for wheels he ordered 4 1/2 backspace but they stopped making them and he went with 4 1/2 instead...
think he is running a 225/50-17 up front and something a hair wider but same height in the rear..