Does anyone know if it is neccessary to drop the fuel tank on a 73 to change the fuel sending unit?
I have removed the sending unit on my '71 (same tank and sending unit as your '73) without dropping the tank.
While you're under there, be sure to replace EVERY single piece of rubber fuel line. After 30+ years, the rubber is brittle and cracks/breaks very easily, so since you're in that vicinity, it's a good time to take care of it.