I think that belt number should read: 25080537 (Can also be shown as 25-080537.)Yep..38504 is the napa number for the tensioner and the belt is 080537. Napa rocks.
It's the number the cummins belt crossed over to in NBH, and it's the one I got and installed on mine.. The NAPA on Magnolia (not the warehouse) had 3 of 'em in stock.