CiES makes magnetically based fuel floats that are supposed to be more accurate and consistent than the resistance based floats we currently use.  Their floats are currently used in Cirrus aircraft.   Just for grins I wrote and asked if they plan to make their floats available for older certified aircraft, specifically Mooney.  They wrote back and said they have a design and verbal agreement with Mooney so stand by.   Combined with a compatible indicator such as that made by Aerospace Logic,