The best way is to move the springs, get the wheels and tires you plan to run, and cut the rear to fit. It's the only way things will be prefect.
This is exactly what I did and my car acme out just like I wanted it. I also agree with using the minimum back space, it makes getting the tire/wheel off easier.
I made a fixture of angle iron, a long narrow rectangle to set the tires and wheels in. With the car on jack stands I raised the tire/wheel up and slid the fixture under them and used a floor jack on each end raised the tires and wheels up into the wheel wells. Then it was just a matter of centering them in the wheel well and measuring for the rear end. Remember to subtract brake drum or rotor thickness from the measurement.
