My :
If you rewire your car any way and stock looking is not mandatory...

... I would consider to move the "connector" into the car under the dashboard and close the connector's hole (there are delete plates available or just make one yourself). It takes a grommet (and a hose) to guide the wires into the car.

Inside the car you can take whatever you want (to connect wires) since it's not necessary to make it weatherproof. You could take simple screw-type connectors which make everything much, MUCH easier . No soldering, no crimping, no costly parts, no thin wires, no weak terminals that heat up. You can place the (modern!) fuses where you can check them without removing the drivers seat even if you're older than 25 (you could place them in the ashtray as an idea).

Another hint: If you "paint" your car (anywhere) take care that there are enough places where electrical grounding can happen . If you paint parts that were bare metal before, you may lock grounding connections!