I have a 65 Cutlass with a 455 engine (73-76) and I am a bit confused on the engine wiring.
From the starter I have three wires:
- Thick Black
- Small Black
- Yellow
The Thick black wire then routes to a junction box / horn relay switch and the other two connect to a connector. From the junction box a thick cable goes to the ground- connector on the starter.

From the alternator:
- Thick cable to Pos+ on the batter
- connector with two wires black & red


Does this seem correct? Shouldnt the starter go to the pos+ connector on the battery and the alternator to neg-?

 

Did you ever determine what type of alternator you have? Look at the two wire plug going to the alternator. If it is flat like this, it's an internal regulator:

If it's square like this, it's an external regulator:



I'm going to assume it's the first with the internal regulator. In that case, the heavy red wire from the threaded battery post on the alternator goes to either the + terminal on the battery or to the threaded post on the junction block. Either is acceptable. The small red wire also goes to the junction block. The black wire goes to the brown wire coming from the GEN light on the dash. This brown wire will be in the harness that comes from the firewall connector and it must be used to ensure the alternator turns on and starts charging.

On the starter, the heavy battery cable should run from the junction block to the threaded post on the starter solenoid. Of the two smaller wires, the thicker of the two should come from the ignition switch and should run to the "S" post on the solenoid. The other should run from the "R" post on the solenoid to the + terminal of the ignition coil.