It could also be a Dana setup. Is the rear center section round? Or oblong looking with one side much larger than the other? Dana's were one tough as hell rear end, and I believe they had a 9 3/4" ring gear. But the ones in the trucks aren't really applicable for performance usage. If you look at the truck, it's likely a 6 or 10 bolt lug pattern, denoting 1 ton or larger.