Last one I installed was on a 2000 Jimmy. Left the factory anti-theft as is.
You can use either key fob to lock or unlock the truck, without any interference from the other system. You can arm the factory, arm the aftermarket, hit the start button and everything works fine.
Ive seen quite a few fail in my years. If you want someone to do it right take it to Cartronics on Brice Rd, ask for Tony Barker, tell him we sent you.