I looked at them a few years back. Make certain you have a good towing capacity. The Allison Transmission they put in made the determination. Don't recall the exact difference, but there was. The ones I looked at were right at the max weight for the vehicle after they put the custom body on and the upgrades in the cab. Good luck!
2007 38Rl3 MS
2005 Chevy 3500 4x4 5" Exhaust, Edge Attitude Tuner, Airaid Intake, Air Bags, Rancho Shocks, Hellwig Big Wig Sway Bar