GM-GMC: tires, wheel toy, stock tire

Question
I have an '02 Sierra 2500HD w/6.6 Duramax.
I have been advised by a couple of different sources, to up size the tires when replacing them. The stock tire is
LT245/75 R16. Was told to go to a 265/75 R16. I plan on pulling a large 5th wheel toy hauler with this truck and will be replacing the tires soon. Is there an validity to their suggestion?
Thank you for your time.

Answer
Often upgrading tires is purely a cosmetic upgrade.  There is no harm in changing tire size, you can have your BCM updated with the new tire size so that everything will function as designed.  One thing I would keep in mind is the load rating of the tires you are putting on, if you are pulling a fifth, you will want a good HD tire.  Hope this helps.