Dash Power Feed Confusion

@Mattax To address some of your questions. I know the car was a canadian build, and yes it does have a rear window defroster which could be that mystery wire. The 18ga yellow wire runs to a switch and relay which wasnt stock, looks to be for an aftermarket something or other. I was going to use it for a fuel pump but I will re-wire the feed properly from a better source. There is a fusible link in the larger red wire you labelled as "from battery" at the ignition relay. The 16ga one you had circled with the blue tag and link runs to the ignition relay aswell but it goes directly to the coloumn connection after the firewall. I will have to do all the continuity checks and get some more pictures in a couple weeks as I am out of town for work. But I appreciate all the help so far. Its making more and more sense.