I'd go with 4.5" in the front and 5" in the rear. That size tire in the rear may be difficult to fit, unless the car sits really high in the rear. I had 225/40 18 on the front of my car with 4" backspacing and they fit fine, at full turn the tire would just barely hit rub the frame. If you get the 5" back spacing for the rear you may have to mount the shock inboard the frame. My best advice is to put some tires and wheels on the car now, find out the demensions of those tires (like the section width)and measure how much room you have, like space from the tire to the shock, tire to the frame, tire to the inner fender etc. Then find out the demensions of the tires you want to put on the car and see if you have enough room. Make sure you leave enough clearence for move ment of the tire due to cornering or going up an embankment, I would think you should have a minimum of 1/2". You can also try searching the archives in the tire and wheel section of this board, also I beleive there are a couple people that visit this board that have the same tire wheel combo you want.