I just talked to Magnaflow, they DO have a single(#15845) dual(#15847) exhaust kits. for the 5.3 V-8 crew cab(not the lowered sport 2 wheel drive). Prices #15845 $650.00, #15847 $750.00. You can't keep the spare tire in place with the dual. 1-800-824-8664 Calif. I called K&N also, no luck, only filters for the factory choke box. The price for15847 is $583 and change at Summit and Stylin
Are you talking about the new Canyon/Colorodo's with the 5.3? If so cool. Maybe you can modify you stock air box, cut some holes in the front and fender side and smooth out the inside ribs.
Slp uses alot of factory style closed boxes, it's worth checking out till K&N comes out with a kit.