Here's the deal, my 3500 is failing me in a few areas of towing, and im trying to upgrade to a 4500 or 5500 but am being told I just cant have what I want. Why is it I can order a 2 wheel drive 4500 with an exhast brake, but I cant have a 4X4 4500 with an exhaust brake? I need both and just can't do with one or the other. Ive been warned that if I put an exhuast brake on a 4X4 4500 or a 5500 it will void the warranty.....

Also, any suggestion on where to buy? Im not real happy with some of the answers ive been getting locally..