'68 Barracuda -wire to fuel tank sender

the wire going to the sender is a 5 volt reference voltage that pulses on off.
Yes there is a connector for it behind the
left kick panel. at the tank there is a short
piece of rubber hose connecting the fuel line to the sending unit and fuel line is at chassis ground potential and the sender isn’t. therefore the sender and fuel sending unit are insulated
from each other by the short hose hence the reason you need the ground strap shown above to give the sender a reference to ground.