* GM 7.5-inch 10-bolt: This was a common, relatively lightweight rear axle.
* GM 8.5-inch 10-bolt: A more heavy-duty option, often found in performance models or those with optional performance packages.
There were also less common options, and whether it was a posi-traction (limited-slip differential) unit or an open differential would depend on the specific vehicle's options. To know for certain what rear end is in a *specific* 1984 Camaro, you'd need to check the vehicle's specifications, build sheet (if available), or physically inspect the differential itself.
