What size tires should be put on my truck if I put a 2 1/2 to a 3 inch lift on it?

A 2 to 3 inch lift will not gain you much tire clearance. A couple of sizes up from stock should be about all you can do.

Ask & or go to Discount Tires, they are very good with oversized tires & most probably done that same thing for a customer before. Dont forget to tell them what size wheels you have too! And a good time to buy new biggermag style wheels there too if you can afford them, I put 17's on my 1995 sb Chevy truck with Nitto 50 series tires staggered 225X50XR17 front & 255X50XR17 rear, & a 2 wheel drive like yours, but a 4-6" lowered race truck.