I remember a thread about converting to a capacitor fuel level sensing system.
I think the key is that the system would use the same 20 - 220 ohms. I have looked at the Stewart Warner system that is 35 - 240 ohms and that is the only issue I can see. The Stewart Warner system has a mounting plate you can put inside the tank for the backing plate for the screws and mounting nuts. It also has fuel gaskets for both sides to make sure of no leaks. There are a couple of 3rd gen threads about OEM tank vent fittings at the same mounting location that leak water into the fuel tank, but they are not well mounted into the fuel tank body. I think with the steel backing plate, gaskets, and enough Permatex Black RTV you could seal that mounting area without question. On my 2002 there is even a tank moulded flat location to mount it just forward and up from the removable canister. Very enticing idea though. I would need help in developing a resistance circuit that would make 35 - 240 look like 20 - 220 so the OEM gauge would read as correctly as it does.
I'll go back and see if I can find that thread on the capacitance fuel level sender.
https://www.turbodieselregister.com/forums/showthread.php?t=165333&highlight=capacitance
tractorface in the following thread states he did a capacitance system
https://www.turbodieselregister.com/forums/showthread.php?t=120094&highlight=capacitance
This one has a great fix to the OEM sender mechanism and a really good pic of the fix and a DC part number of JUST the fuel level rheostat.
https://www.turbodieselregister.com/forums/showthread.php?t=105129&highlight=capacitance
Here tis - thread reply #13 is the capacitance probe and where to get it correctly built to our system 20 - 220 ohms, however read on and he had to change the wire harness somehow.
https://www.turbodieselregister.com/forums/showthread.php?t=110157&highlight=capacitance
BTW I have 1 of CStewarts fittings that I was going to use to do a 3/8 pickup like he did, but did the DrawStraw instead. I do not need the CStewart fitting now if anyone is interested. It is like the DrawStraw metal fitting but with only 1 @1/4 npt threaded hole. PM me if interested.
I even looked at TEMPO marine fuel reporting systems. They have a mechanical gauge that you can add an electrical readout sensor unit to it. (I think I am going to use the mechanical gauge only in a bed aux tank I am about to do) However, it works back to 35 - 240 ohm (the industry standard) and the OEM fuel gauge would not read correctly.
GARY - Any ideas on a resistance circuit to subtract a resistance value over a range of resistance? ie 35 - 240 ohms -> 20 - 220 ohms?
I like the Stewart Warner system, very industrial strength, well made unit and Stewart Warner has been in the fuel level sensing business a long time. Just the wrong ohms.
Of course you could mentally adjust what the OEM gauge reads with what is actually happening in the tank.

Less than full on OEM gauge (35 ohms)= full actual tank level; empty on OEM gauge (220 ohms)= not quite empty actual tank level. It would provide a safety margin on the OEM gauge though. The "low fuel" light would come on early but you would know it reads less than actual and you could go probably to OEM gauge empty and still have the 10 gallons remaining like we do now when the "low fuel" light comes on.
My OEM gauge reads full until I have used about 1/4 tank because the OEM float is 1 1/2" UNDER the surface of the fuel when the tank is full and has to sit under fluid level until the fluid level is used and it can actually "float".
Bob Weis