I have has some recent problems with my wheels rubbing in my wheel wells whenever weight is in the car (98 SVT), i went to the ford dealership after the third attempt of the mechanic at the place i bought the car didnt fix it. Ford Dealer tells me I have the wrong rims on the back tires. turns out the back ones are 7 inches wide when the car needed 6.5 inches. they look ALMOST exactly the same the back ones dont have a lip around them while the front ones do. Is this true about the width of the rims?, Cause i went on tirerack to look at rims and all the ones that came up for 98 SVTs were 7 inches wide.
Might check where the rear bumper merges with the wheel arch to see if there is lump there for the fastener. You can push this in/up slightly to provide some extra clearance in the wheel wells. A few whacks with a rubber mallet may clear up your problem if that's where it touches.