Is that cable attached to the frame on the drivers side? If so, you could probably use C-body rear cables where the passenger side rear cable is long and crosses over the rear axle and terminates on a bracket on the passenger side frame; the driver side rear cable is shorter and terminates on the same bracket. An equalizer bar connects the two rear cable ends and attaches to the threaded end on the front cable.
That's a great question. I don't know where it attaches because it was just tucked up and wrapped around the frame connectors when I got the car as a roller. I have no reference point as to where it is supposed to go or what bracket it uses on an A-body. I think it does go down the driver's side and the there's probably a connector/equalizer that's supposed to be there. I think you're right about the longer passenger side cable. I've looked for diagrams for 68 A-bodies that show the cable paths but so far have not found any.
I'm thinking about trying to buy a used set of B or C body cables and see if I can fabricate something.
