I might be in the market for a truck in a couple of months. The problem is that I will need a longer wheelbase than is offered in a 3500 but I don't necessarily need the added suspension, weight, height, etc. of a 4500 or larger truck. We are currently running all Dodges and 3 of them have stretched frames with the longest fitted with a 20ft box. The question I have is will lengthening the frame to fit our needs void any and all warranties on the truck? Would they say, "your engine failed because of the extra load the truck was carrying and the truck was not designed for that." Or am I going to have to go with a 4500 or Freightliner or International with the proper frame length?

Thank you.

Get with a dealer specializing in commercial sales, they may know an upfitter that GM will drop ship the truck to, IIRC 3500 only has 8' rails, even on chassis cabs

What are you stretching the wheel base for? I think you might just go with the 4500 and save the trouble. Then you can have a hauling machine that you can do anything with... IMO ..