Tires: Load Range for trailer towing, 5th wheel trailer, 2007 gmc 3500

Question
I have a 2007 GMC 3500 Classic long bed, SRW (single rear wheel)that I tow a 39' 5th wheel trailer with.  I need new tires, but would like to use a tire with a higher load range rating.  Current tires are 265/75R16 load range E M+S.  I plan on doing extensive traveling next couple years.  The SRW hasn't been a problem, but several folks have cautioned me that the SRW could be a problem if the side wall flexes during sharp turning or breaking.  I don't want to trade up to a DRW #$$$#.  I have the Duramax diesel and Allison transmission.  Are there tires with a higher load range?  I don't know if taller or wider tires would be better or not.  It looks like I have room in the fender well for larger tires.  What would you recommend?

Answer
Mark,

The problem you will encounter is that in order to go up in load carrying capacity, you also need to go up in size.  Unfortunately, the stock rims on your truck are 7" wide.  If you want to put a bigger tire on the vehicle, you will have to buy wider rims.

But if you're OK with buying rims, the contact Tire Rack or Discount Tire.  They have the measurements of the fenderwells and can tell you what the biggest tire is that will fit.