While I don't have a full sized truck (just a lowly Ranger 4x4) I have had really good results with Toyo tires (using the Open Country model now)... First set got me just over 60k miles (guaranteed for that long) with my lead foot. I left a good amount of tread at stop signs while I had them, and didn't baby them one bit. I replaced them this summer with the same tire. This time, it's guaranteed for 65k miles.
I would look to see if there's a Toyo tire that fits your used model, and budget range. I blew about $800 on the four of mine. BUT, that included a 4 wheel alignment, and such. I'm getting better gas mileage since doing the alignment... The store I went to isn't in your area (Town Fair Tire) so you'll need to source them out on your own... I think Tire Rack has them. Get your preferred grease monkey to install them for you.