Rear Pinion Seal

I need to replace the rear pinion seal on my '98 Jimmy. The ID tag is missing from the 3rd. member. How can I tell if I have a 7.5" or an 8.5" rear end?
The vehicle has the Towing Package if that helps.
Thanks.

Call your local GMC parts counter. They helped me identify the rear axle. Most important the seal was a lot cheaper than Autozone or Advanced Auto Parts etc.

Got it done, Thanks. I have the GM 10 bolt 7.6 rear end. And NAPA had the seal for $14.00.
Sleeping better. :grinyes: