William,
For decades we have used the Shadin fuel flow which also tracks fuel consumed and if hooked to a GPS, gives you gallons to destination. With the Osborne STC, it can replace the fuel flow gauge that came with the Comanche.
http://www.shadin.com/products/fuel-flo ... /digiflo-l Some folks have chosen to leave the Piper Fuel flow gauge as a backup.
Even with the Shadin, if the flight is long enough to require a tank change, I still use a paper log for how much has been burned out of each tank and what remains in each tank.