NADA type benchmarks for heavy truck

Long time lurker and past frequent poster here guys. I've decided to take a turn in my career. I had previously worked about 15 years in automotive parts management (Honda, Hyundai, Mazda) and need a little help. I decided to take on a medium/heavy duty fleet maintenance company's mobile parts inventory (100+ trucks in 20 states). I am also starting to help manage our parts inventory in our brick and mortar shops. I was wondering if there were something like NADA parts management guidelines/benchmarks for the medium/heavy duty side. Keep in mind that I'm not part of a brand/franchise. This company DMS doesn't come close to any that I have been on (ADP, R&R, UCS, and Dealer Track) in a bad way and reporting/knowledge of inventory management is non almost non-existent here. I guess that's why I'm here! I know how to get all of the figures needed, but I need a baseline. Thanks for all your help.
BTW...I have both of Mike Nichol's inventory books from the auto days...the yellow one and the white one!!

BTW...I have both of Mike Nichol's inventory books from the auto days...the yellow one and the white one!!