I know on F-Bodys you can ground the relay wire of the fog light relay and make your fog lights stay on with your high beams. Can you do this with the trucks. I want to do this to my 04 Sierra 5.3 like I had on the Trans Am.

 

There are ways to do it... though im not exactly sure if they way you said works or not. But there are kits that splice into your stock wiring that do the same thing. Look for R&D performance

 

Do a search over at fsc.com I saw an article about that.