Rally dash redo
More than one circuit supplied by a single fuse is typical. So rather than to route so many wires out of the fuse box to different things, a single wire for radio or wipers will connect to a jumper to the next circuit such as reverse lamps. 67 used wiper fuse for reverse lamps. 68 used radio fuse for reverse lamps.
Why? Here's how I see it.. A short circuit in wiring to reverse lamps could blow a fuse and disable the windshield wipers. Reverse lamps is a lot of wire too. "I backed over a tricycle and now my windshield wipers don't work".
They moved those reverse lamps up and out of harms/tricycles way (for 1 year model).
At the same time, 68 model will have reverse lamp wiring to a switch screwed into the trans underneath the car, with connectors on either side a of a brown neutral safety wire that is in itself a short to ground.
"Lets have that short circuit disable the radio instead."
They didn't spend money to change things just to be A-holes.
So what will you do? Cut the white wire out of radio connector, route and patch it into wiper connector?
I would probably just verify reverse lamps properly connected/supplied by the 68 radio wiring and connector. I'm going to make and print a diagram showing my changes to keep in this car anyway.