2 1/2 ton ESP program is the "Extended Service Program", expected life on these trucks was supposed to be 12 years in a non-comat role. Obviously they've served much longer. Now they are (were?) taking and refurbing some of the older trucks into the A3 models. I believe the stock wheels are 20x7, I'd go measure one if it would stop raining. I've only seen one set of those wheels on the surplus market, that was on Ebay and they went for big $$$$$$$.