i just put a 270 in my 40. i didnt touch the electrical system. when i turned on the key the fuel gage was past the full mark. i know it wasnt right because there was only two gallons of gas in the tank. i checked the resistance on the sender to ground and i got nothing. wtf i didnt do anything to lose it. checked from sender wire to fuel valve at the tank and got 2 ohms. i dumped five gallons of gas in and i got 8 ohms but only when i had the sender wire via a jumper to the tank shut off valve. i lost my ground, how did this happen. when i put the engine in i ran a new fuel line from the tank and the fuel pump and add a plastic filter close to the shut off valve. the rubber fuel lines are what broke the circuit. after i ran a seperate wire from the sender housing and grounded to frame the gage read 1/4 tank.
before that the fuel line was the ground.

maybe when you replaced the float you lost your ground.