* 8.5-inch 10-bolt: This was the most common rear end used in the 1991 Camaro. It's a relatively lightweight and common differential.
* 7.5-inch 10-bolt: Less common than the 8.5-inch, but some lower-trim Camaros might have had this smaller and lighter rear end. It's generally considered less durable than the 8.5-inch.
To know for sure which rearend is in *your* specific 1991 Camaro, you'd need to:
* Check the Vehicle Identification Number (VIN): Decoding the VIN can reveal some specifications, but not always the exact rear axle type.
* Look at the differential cover: The cover itself might have markings indicating the size (7.5 or 8.5 inch).
* Measure the differential housing: The physical diameter of the housing can give you a clue.
Without more information about your specific 1991 Camaro, it's impossible to say for certain which type of rear end it has.
