I have a red wire comming from the transistor box on the pass side wheel well. There are actually 2 red wires and one goes into the wiring harness. This wire is about a foot long and has a connector on it. I just put the motor back in and dont remember where I pulled it from.

 

My neighbor has a '68 and his amplifier is mounted to the LH inner fender towards the core support and this is where I remember them to be mounted on C2's as well. I suppose the harness would reach to the RH side, but don't know why anybody would change the location? Are you sure you have all the correct parts for Delco TI? The harness should have 3 wires, you mentioned only one wire?

We just rebuilt his TI distributor so the wiring is somewhat fresh in my mind. I'm sure the shop manual has a diagram for reference. '68 used 2 different amps and harnesses. Depending on how the amp receives battery power either from the ignition switch or the starter with the later design having a weatherproof plug on the short harness (pink; gray; black) that plugs into the amp and into the main amp harness and there will be 2 pink wires at one point in the harness. The later style harness will also have an additional connector for the old style amp. The main harness plugs into the short harness from the amp, goes into 2 splices near the firewall and then to the distributor with white and green/white wires. If you stretch out the wire you have, where does it reach to? Hope this helps.