I actually learned about the universal sending unit swap via my searching on the forum; thus, I can't credit for the idea or the research:
http://forums1.amceaglesden.com/index.php?topic=35168.0I did have to modify the sending unit electrical pickup due to the tank configuration of the SX/4 so that it sits at a 90 degree angle to the bracket. Thankfully that modification only entailed one screw.
The biggest challenge was actually getting the unit into the tank. I ended up needing to partially disassemble the sender with half of it in the tank to get all the parts to clear the opening. Then I bolted everything back together. It's kinda like building a ship in a bottle :-) I'll take and post pictures when I remove the sender for further calibration.
The other important thing to remember is to make sure that the center post does not make contact with the body of the sender as it will complete the circuit thus resulting in an eternally full gauge reading.