The load range you get really depends on what you do with your truck. If you regularly haul heavy trailers, I would suggest you stick with a load range E tire. I know there are load range D tires that have a higher weight rating than the stock load range E tires, but a load range E will have stiffer sidewalls and be able to go to higher pressures which gives them a little more stability when loaded heavy. If you don't every haul anything, lots of people get away with running an XL load rated tire. The only catch to that is there are some tire stores that won't sell or mount them on an 8 lug wheel (Discount Tire is one I know of).
Most tires available for our trucks are going to work just as well as any other tire at different temperatures. Obviously a cold tire won't grip as well as a warm tire which will grip better than an overheated tire, but there is no way around that. In sports cars, they make tires that are almost undriveable in cold weather, but there aren't really any tires available for our trucks that have compounds with those characteristics.
Typically, rubber compound will change with tire manufacturers and tire model. So a 31" tall tire should have the same rubber as a 37" tire that is from the same line and manufacturer.
As long as you stick with a name brand tire, you shouldn't have any worries about heat or speed ratings.