Where does this electrical box go?

I agree with the matching driveline, and I believe as delivered the electrical system was adequate.
Proof being my 1969 didn't have an issue until 2015. Not sure what caused it. Maybe a PO's failing battery that left the alt running max amps all the time trying to top it off, or an aging wiper motor creating a higher load, or unseen corrosion inside a wire, just not sure. My point was if you are going to upgrade the charging system, as delivered, the rest of the electrical system isn't adequate, and the bypass isn't responsible for that.