The GMC's have even less room then the Chevy's on the 99-02. Pretty much no room to put even a 3" intercooler in the grill and for that you would have to cut all most all the plastic out of the grill, or cut the hood latch support out and replace it with the intercooler. I have a 24x11x4 core cx racing on mine in the lower valance, but I notched my frame rails a long time ago before the narrower CX coolers where available.

 

I put Brandon's Treadstone intercooler right up front on his 01 GMC, the guy you dropped your turbo kit off here with. I thought it turned out pretty good. It's only hacking if it looks like crap when you're done