Back up light harness

The bulk head connector far right is primarily the wiper motor harness connector. It has space available for other circuits so the factory poked a neutral safety switch connection and reverse lamp wires in it. These connections varied with automatic and manual trans builds until 1970.
if someone parting a later model was willing to put forth the effort they could carefully remove those 3 wires from bulkhead to 3 post neutral safety connector for you.

Being a 68 model car I dont think the neutral safety lead passed through the bulkhead connector for any build. That models single neutral safety wire went directly to the starter relay. Its routed along side of the light harness but not taped in. The reverse lamp wires for that model are inside the car unless it had a manual trans.
I haven't pulled out the schematics to see what you are seeing. Just stating from memory. Hope it helps