Switches, connectors, control units in 72 A body
You have a shop manual? Download a 72 (and others!!) fer free here:
http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=manual%2C+download
der linky
[ame="http://www.abodyjoe.com/pictures/Misc.%20car%20info/1972%20Plymouth%20Chassis%20Serv%20Man.pdf"]http://www.abodyjoe.com/pictures/Mis...Serv%20Man.pdf[/ame]
For the harness, for me, would be a no brainer. Put in the 12 circuit, get rid of the bulkhead connector (or run wiring straight through) and convert the ammeter to voltmeter
Ideas on ammeter to voltmeter, a simple project:
http://www.forabodiesonly.com/mopar/showthread.php?t=119480&highlight=ammeter+conversion
On mine, I used a "used" Painless harness I got cheap, that someone had abandoned a project. I left such connections as the wiper connector in place in the bulkhead, and ran other wiring through the vacant connector holes
Mine ain't all the pretty, but I used a Voyager relay box, and you can buy new ones made by Bussmann which you can configure the way you want, for the underhood loads, ignition/ charging, fuel pump, high and low beam, and an extra for security, as well as a couple of spare sockets.
This one mounts very nicely to the front fender apron between the battery and washer tank
Some of this will also depend on whether you want a trunk mount battery, and plan on ever showing up at a dragstrip, as you must have certain safety 'stuff' in regards to a trunk mount battery