OK, so I finally have the truck and it looks great but I am not sold on the tires that are on it. Currently the truck has P265 75 R16 with a Load Range E (3415lbs single) and they call for a PSI of 80. Now, I have a brand set of P285 75 R16 with a Load Range D (3305lbs single) and they call for a PSI of 65, and these are on another truck I own that is for sale.
So, my question is, can I or should I swap these before the sale?

Let me know what you think.

the 265s will probably get better mpg but 285s (33s) look good on these trucks........your call. What kind of tires, just curious?

Bigger is always better,lol swap'um

The truck currently has the Dunlop 265's on it that are load range E and I would be looking to put Michelin 285's on that are load range D.How much do you think this change would decrease fuel mileage? Any concerns with the change in load range?

I don't think it would change more than 1 mpg, probably not even that. If you've got a set of good Michs, I'd definately put them on there over the Dunlops. I personnaly wouldn't worry about E. vs. D in this situation.

Definately go with the 285's.