65 Dart gas tank leak

Not sure why you think you need the outlet at the bottom of the tank. The sender sock already sits on the floor of the tank. The main related issue is that it is best to put the pickup in a sump so that the pump doesn't suck air when the fuel is low and sloshes around. Next best thing is a surge pot surrounding the pickup.

The Dart tank is already a bit like that, with the recess around the spare tire forming a wall. It should be much more immune to sloshing than the wide, shallow tank in my 65 Newport. When I get low on fuel there and stop suddenly, I can hear my EFI pump chatter as it sucks air and the engine stumbles.