Rear Suspension Problem

[HIZNHRZ]

I was recently standing behind my 91 ZR1 looking at the back end I noticed it is not sitting level. When parked on a level surface the passenger side of the car sits higher than the drivers side. From a side view, the space between the top of the rear passenger tire and the bottom of the rear fender is more than an inch higher than the same space on the drivers side.

Has anyone had a similar problem or seen this before?

The car has never been hit. The rubber bushings on each rear suspension piece are all original but appear to be in decent shape. Even if they were each dry rotted and distorted I can’t believe this would cause the car to sit an inch higher on one side than the other. The one thing I find suspect is the composite leaf spring.

How do you determine if the spring has gotten weak?

If I start taking anything apart, I’m thinking about replacing the rubber suspension bushings. Any suggestions whether I should use factory replacement rubber or polyurethane? Also, if I have to replace the spring, any thoughts or suggestions on replacing with a stock or aftermarket piece?