12v with key on

I would use a relay. Your answers are in the service manuals. You can download some years from MyMopar. Some of the manuals there came from the guys on HERE


There are only two 12V sources switched by the key, that is "ignition run" (ign1) and the switched accessory wire going to the acc buss in the fuse panel. The fuse panel has THREE busses.....

1......"hot" on all the time for such as brake lights
2......."ACC" switched by the key
3.......The "trick" fuse for the instrument lamps. This fuse is powered FROM the instrument dimmer control, which is powered off the tail lamp circuit. That is identified by the fuse at one end of the box, with a "bunch" of orange wires. So stay away from that

For your added panel, what sorts of things and what kind of amperage do you expect to draw? If you have a stock ammeter, "it might" be too much to pull off that. One place is to power the relay contacts off the starter relay stud. You will have to "make" a path into the interior. I would put a "master" fuse/ breaker as close to the battery connection as you can