Engine Bay Electrical Slant 6

He did what many recommend, which is to put the lights on relays, but didn't do an elegant job. He also put the starter and horn on the same generic "automobile" relays. It looks like he left the harnesses for the ignition and wipers untouched. He mainly just hacked into the light harness. He added extension wires for the horn and starter relays to move them off the fire-wall. I did similar, but mine is prettier, with a Power Distribution Center next to the battery and all wires in smooth sheath.

To fix, you can get just the light harness from a donor car. You can still buy new starter and horn relays. I used a 74 Dart for re-wiring my 65 Dart so I could keep my factory harness unmolested. I did remove the bulkhead connectors since those are different (latches and keys vary). You can remove the spade pins (56 terminal males) easily by compressing width-wise and wiggle them thru. Sand them off and coat with dielectric grease before installing in your connector housings.

Follow the wiring diagram. You just use short wires to the firewall relays. If you can't find the special vinyl tape wrap (not gunky electrical tape), you might use self-fusing silicone tape, but it will be thicker. Your ballast resistor is missing, but might mean you have an upgraded ignition. Consider replacing your old voltage regulator with a new electronic one. I see ones with the same connectors for ~$12 currently, though thin and shiny. Your black box could actually be the new electronic type (some were disguised to look original), so look underneath. If large wirewound resistors, it is the old mechanical type. While you have everything off the firewall, sand away that rust and re-paint.

Also read up on the problems with large ammeter currents flowing thru the spade connectors and solutions. I don't have that problem since in 65 they used dedicated round feed-thru lugs for those big wires. They dropped that plus upped the current draw, not a wise decision.