Major rubbing issues

[Kamaro Killer]

Ok, I may get a lesson here, but, oh well. What are quad shocks? I am having problems with rubbing. I have a 93 5.0 with 225/60/16 tires, on pony rims, and the car is at the stock height. I also have a flowmaster cat-back exhaust system. My back left tire seems to be rubbing on something, very badly. The inside of the sidewall is what's wearing out, so I'm assuming it's not just the alignment. The only thing I noticed that might be rubbing is the tailpipe, right where it curves for the last time, before exiting the rear. The tailpipe is moved over as far to the center of the car as possible though. There is a shock, (not the main rear shock) going from the top of the inner fenderwall to the side of the frame, and it's close to the wheel, but I'm not sure if that's what's rubbing. Here is a pic. Thanks, Keith