Painless?

I agree with HotRod to a degree. If you plan and increasing the load to the system via cooling fans, stereo, and other components, I’d replace the system. We are talking about almost 50 year old wiring. The bulkhead / Amp gauge by-pass should be done.

As for the painless, the Mopar 21 circuit #90542 takes some work and is by no means “painless” the first one you do is always a PITA but well worth it. Go and download the 90542 instructions and read them about 25 times before you decide to start the project. After that it is easy. The one thing that sucks about the kit, is you “rebuild” all of the light sockets for taillights and markers and such. Kinda a pain in the butt. The wire is of good quality, with it color coded and marked each foot or so. Take your time, alway leave a little slack at the end of each run for service or mistakes. And for the love of your higher being, don’t use wire nuts and get yourself a good set of crimpers/strippers…