97 Tahoe factory Locker or Posi?

I am looking to buy a 97, 98, or 99 Tahoe 4door 4x4 LT. I am wondering if any came with a rear locker or posi from the factory. If it's an option how do I distinguise a tahoe with one (besides trying to get wheel spin during the test drive). Thanks

look in the glovebox, there is a placard with all the RPO codes.

The G80 code is the locking rear diff.... if it has the G80 then that is the factory one.