Wheel Back spacing?

Does anyone know what the proper back spacing is or should be on a 68 ford torino fastback?
What I am really looking for is how to put a 9in wide rim with out tubing or moving the springs.

Thanks

On my 68 Torino FB street car I'm running 94' mach 1 wheels(17x8- 5.5 bs) and they fit the rear with room to spare. To get a good reliable answer go to torinocobra.com and search wheel size in tech. section.

Thanks , Do you have any pics?

Here's some to give you an idea of the room you have. These tires section at 9.5, I could fit 10.5 to 11 sec. width.

Thanks for the pics the car looks good . Sorry it took so long to reply back! What size enine and trans are you running?

Worked over 460/c6, about 475 to 500hp.

I have two I am trying to build one is a 390 c-6 car and the other is 302 with p/s ,power disc brakes, and a/c. both are green with the gold strip. i will post some pics later.