Tires and trailer tires

[RMccord]

I have a 2005HD and the current tires are rated at 3042 lbs. I have read here that some have gone up to 265 size tires and they are rated at 3400 lbs capacity.
Will these fit on the same wheels my current tires are on and what pressure would they most likely need. My current tires are at 85 psi.

Also If I wanted to replace the stock Mission tires that will be coming in with my Big Sky in about 6 weeks what size LT tire should I get. I know I would want a G rated tire. What are the preferred ones that most are going to. Goodyear?? Etc. I will use the Missions for a year or so perhaps as for that length of time we wont be going out for more than a couple of weeks at a time. Probably also a weekend a month in between and I hate to toss them right out of the hopper. Maybe replace them up front and store them as replacements.

Thanks