Air shocks and long shackles do absolutely nothing to improve any aspect of the cars performance..... A correctly sized wheel and tire combination, or tubbing the rear to accomodate the size of tire and wheel you want to run is the correct way to do it.

If memory serves me correctly, the right backspacing on the rear wheels and a bit of trimming on the wheel lip will allow use of a 15 X 7 wheel on the back with a 245x60x15 tire. I've seen a lot of cars running in the low 11's with slicks on a 7" wheel..... The jacked up back end look along with extended shackles and air shocks never has and never will work good on either a street car or a drag car.