OK here is what I found out from Fleetguard about replacement fuel filters for 1st gens ( original p/n FS1232 )
FS series are water seperators and generally have a large white drain knob. FF are straight filters and generally have no drain provisions.
FS1232 6. 69" tall w/ sensor or 4. 42" w/o sensor flow is 50 gph 20 micron. Drain and sensor valve is p/n 3831852-S
FF5052 4. 59" ( metal body - NLA ) which changes to FF42000 4. 58" ( this is a black non-metallic body ) flow is 61 gph micron 20. This is a common filter for the "B" series engine in other applications.
FS1235 4. 53" is a shorter version of FS1251 5. 63" but flow is ONLY 19 gph
FF5018 4. 92" flow rate is only 20 gph or Stratapore upgrade is FF5461 flow rate is 20 gph but is 4 micron ( too fine for a single filter ) or FS1221 7. 09" flow is 53 gph micron is 22.
If you want to repIace your stock filter and you don't want to use the WIF sensor/drain valve, then I would use the FF42000. It is a common filter and has a flat base with a 3/8 square hole in it for easy removal. Since you will be using a different filter buy two, and keep one in the truck.
In general if you are broke down in the middle of nowhere and you don't have a spare filter ( there is a lesson in here ) you could go to any Cummins dealer that uses the "B" series ( Midrange ) engines. These dealers include Freightliner, Case, Ingersol Rand, Komatsu etc. Just don't tell them it's a Dodge, you'll just confuse the guy. . Give them one of these part numbers. You should always carry a spare fuel filter with you, but use your spare and replace it. Don't leave it under the seat for years and expect it to be still sealed in the plastic and clean. I have seen people pull out their "spare" only to find it dirty and rusty .
If you use a filter with less flow it could cause problems at higher rpm or under load.
Shadrach