Same here- port eats more and found out the hard way!
The sender in my Checkmate I replaced with one from West Marine. When I went to replace the one from the Fountain I found it the same as the Checkmates. Also got one from West Marine, as they are basically universal. Just have to get the right length arm and adjust the float position. Very easy.

Back to my original question thou, does the port tank have a sending unit? My SC only has a guage on the starboard tank at the moment...

i found out the hard way that my gauges are not accurate...thank god for tow boat us membership. I now know that I have twin 60 gallon tanks...