Removal / replace sending unit

Probably best to drop the tank and do a full job (clean rust, paint, etc). Since the sender isn't an emergency, I would wait until you have time.

I have changed the sender on several Mopars with the tank in the car, incl my 69 Dart. I pulled the tank in my 65 Dart for a full-up job, but I think you could do it in the car. You need to drive the rear up on ramps to get room to see and swing your arms. Wear safety glasses because junk will fall. Make sure the level is well below the sender (<5 gal). Replace the fuel hose with "fuel injection" type. Insure you have a good ground connection on the new sender (sure that isn't your problem with the old one?).