Wheel width question

I have a set of SS springs but am debating whether or not to use them at this time. It was recommended earlier (in another thread) to go ahead and use them so I am leaning that way. The engine is a '90 360 that is internally stock. Only think I've done to the motor is a performer RPM manifold, 750 Holley vac. secondary carb, and full length headers.
I was asking about the SS Springs because if you put those on you could probably put just about any Tire you want on there that will fit from front to back which is in my experience at 28 inch tire. Of course I have a 73 Duster and I actually run an ebody width rear end that's about 2 in out further than your stock one. I have 275 60 15s (Nitto 555's- $60 each less) on 7 inch wide cop wheels and nothing rubs because the SS Springs Jack the car up. The Nitto say they want at least a seven and a half inch rim but it is what it is.
I went to Walmart and bought 215 65 fifteen's for the front for 136 bucks mounted and balanced.
When I had Hoosier 28 10.5 slicks and 8 inch wide rims I had to put a half inch spacer in the front of my spring perch to bring it back to make the tire clear from hitting the front of the rear fender wall..
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