Good luck, and if you have any questions, don't mind helping out my brothers. Anyway, name is Philip and my cell is 478-775-1964 if you have any questions.
I would replace the intake gasket, water pump, flush the radiator and see what it does. If its blowing water out of the intake(common problem), AND the pump, there's not enough pressure to force the water through the block. If I can be of any help, just let me know, thanks....
If its hit 260 more than once, doubt seriously its a head gasket. Those are steel heads on the Vortec's and they usually crack. Just wouldn't want to give anyone false hope. But there's no "true" way to tell with out sending them to a machine shop. If I can help, let me know and I'll shoot my...