I have gen1 tank (33 rod).
I have a 5/8" vent line from top of tank to inlet of fuel filler cap so that air can be pushed out of the tank and back to atmosphere when filling fuel.

Question is, how do I know when the tank is full? Will the gun click and stop automatically like it does with normal cars? Or do I have to watch through the filler tube and once I see gas I stop?

I do not know approx how much gas I have in the tank now. The sender is useless and I don't know my fuel consumption, so my guess is anywhere between 1/4 and 2/3. If I go at fuel station and fill her up, how do I know when to stop?