Sure there are a lot of tire related threads on this forum, but few deal directly with the Interstate B-van on Sprinter 3500 chassis. I just upgraded to Michelin LTX M/S2 tires before my recent trip to Alaska. I had 30,000 miles on original Continentals. The two front tires were worn due to poor alignment and I had a run flat situation on one of my inner duals that really made changing tires a necessity.
I did a quick search and found one really relevant thread on this forum that you might want to read.
Hope this is useful.