Need Help with wiring

Good morning all...Need some help identifying some wires on my 66 GT350. I ordered the electrical assembly manual, but it doesn't seem to have what I need. After years of tape players and add on tachs, I am trying to get everything back to the way it was. Although my tach doesn't work, I still want the wiring correct. What I am looking for is a wiring identification for the bulkhead harness that is more towards the passenger side. For one thing there is a red wire that looks like it connects to the solenoid along with the positive battery cable. Naturally there is power at all times. The wire isn't connected to anything inside the vehicle. Where does this red wire go? Would also like to know where the other wires go also. My radio light comes on with the on/off knob, but the radio itself doesn't work. I want to make sure the radio is connected properly also. Any help or direction is much appreciated.

Tommy
After further review, I think all I need is the wiring for the tach. If I remember right; many years ago, my tach wasn't working, so I removed it for repairs. When I disconnected the tach, my car wouldn't start. Evidently I had to splice some wires together so it would start. The shop at the time couldn't repair my tach, so I reinstalled the tach, however, I see today that the wires are still disconnected and taped up. So, I think what I need is guidance on how the tach wiring is supposed to be. Also, a repair shop for the tach. I have power to my radio, so I guess I need to get that repaired also. Thanks for any help if you can figure out what I am talking about.
Tommy