I believe the Cummins ISC and ISL use the same oil filter, an Fleetguard LF9009 or Donaldson P553000 or Wix 51748XD or Baldwin BD7309. Most filter produces have a cross-reference table to show what filter part numbers are equivalent.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC