You're gonna have to fabricate, or pay someone else to.
To do most of the things you want, you are going to have to get real personal with our two best friends--Bondo and the Dremel.
I had a 97 silverado which I think has the same dash as the 99 tahoe. You can buy a spare dash from the dealer for like $80, or go to a salvage yard and pick one up for much cheaper.
Check out the fabrication section.I am always surprised at the lack of threads about this topic... This to me is the main stumbling block to installing my carPC. Do most people buy kits or something I am maybe not aware of?