Wiring harness problem...
 

All right, so the '73 is in good shape, but one problem... I have a little electrical demon in there, only way to get rid of it right now is to unhook the battery from the car.

But I've looked and everything is fine, I had one guy check it out and said that the harness in the steering column is screwed, so I need a new one, any price of how much? Or whatelse could be the problem?

Sounds like you should do some basic troubleshooting.
1, disconnect negative battery terminal
2, install a test lamp (not led style) in series between battery post and cable clamp end. Make sure all exceries are turned off.
3, If lamp illuminates you have a drain. While still connected remove fuses one at a time till light goes out. When you find the fuse that makes the light go out the problem is in that circuit.
Some additional notes, if after pulling all fuses and the light is still on it could be a shorted pos diode in your alternater. To verify disconnect output wire (the larger one) from the back of the alternator and see if light goes out if it does you need a alternator. Another sneaky demon could be the trunk light if you have one I see this often but you would find this by pulling fuses. Good Luck

Scott (your friendly neighborhood sweeperking)

It actually could be the trunk, the lock on it is hanging there which means it's not closed, and it does jut out a bit, the light could be out but the circuit to it could be live still and draining the battery, only time will tell