285x75x16 should fit on your stock rims. BFG Mud Terrains are decent in mud, terrible in the sand. BFG A/Ts are great in the sand, not too horrible in the mud. I'd personally go with the A/Ts for overall ride quality if you are going to stick with BFG. Had some really good Michelin A/Ts on my Z71 that will last just about forever and had a fairly agressive tread. If you want good tires, buy Michelins.
