I run the NAPA 1724 also. It is a 2 micron filter, DPP only lists 3micron and up on their cross reference. ALso it only costs about 25-30 bucks and the NAPA by my house always has tons of them in stock. I think the filter is made by Wix.
As for the "stock"filters I assume u could order them from DPP and you could get the Fleetgaurd equivialants from a Cummins dealer, but from what I have heard is that the Fleetgaurd filters are pretty spendy. I would think that you could get the Cimtech ones from a big truck dealer too.
FYI these are hydralic filters, not "actual" fuel filters. They are higher quality than a fuel filter and stronger construction, which is why I think DPP went with them. Also easy to find.
Hope this helps,
J-