how do i know if my 91 is a zr-1 or not?

The following are quotes from the website below. http://www.mcsmk8.com/zr1/90ZR1.HTM "... the tell tale sign of a ZR1 is its extreme width in the back. You cant miss it! It is 4" wider that a regular corvette and uses the massive 315/35/17 tires on 11" wide wheels." "There is an oil cooling system that is larger than most cars entire cooling system. The car has a special version of the German built ZF 6 speed transmission, another radical move on GM. The car has a self adjusting suspension, known as the "FX3", and even more."

Correction: the rear end of a 1990 - 1995 ZR-1 is actually 3 inches wider. If you measure the black spacers between the backup lights and the license plate - each spacer is 1.5 inches wide. A ZR-1 has unique body work starting at the doors and going back. The doors start to widen in the middle flowing into the rear quarters and bumper which are unique to the ZR-1. Of course the best way to tell a ZR-1 apart from a standard C4 Corvette is the presence of an LT5 engine under the hood, and the VIN which was unique to the ZR-1. More info: http://www.CorvetteActionCenter.com/specs/c4/zr1/