I got the switch because my car sits for a while in the winter and I wanted an easy way to disconnect the battery. It is also helpful for working on the engine, all I gotta do is turn the switch off. I got the switch from Boaters World but if you look here there are some different types. I just got mine from boaters world so I didn't have to order one (i'm impatient).
As for hooking it up, I just used the negative terminal .. connected to one side of the switch and the other side to the battery. I will see if I have pics of when I installed it. I also had to make a mounting bracket for it. This was easy, I just got a piece of sheet metal from Lowes, cut it, drilled the mounting holes and done. Glad you think it is interesting.
the most heavily rotted car I ever saw was bought by a guy here in massachusetts and shipped from hawaii. it was a 87 grand national and it was so rotted that even the door posts was missing sections. I was afraid to close the door. I have no clue why he bought this car it was awfull
my guess is the car spent a little time on the ocean bed out there and then was sold after it started falling apart.
Here is the cheapest route to take (which I did): Buy some brass battery terminal connectors ($3) from Kragen/Autozone, etc to replace the old corroded leads on your harness and clean the exposed wires well on the harness. Clean your terminals and battery box with water mixed with baking soda (NOT baking powder). Use a cheap battery terminal brush to clean the posts. Felt washers and battery spray/grease ($4-6) is the last step.