Interesting. I do not have that little firewall junction connector on my 68 Coupe, but it does appear the big orange line does go into the firewall on yours. I'd guess it was convertible-specific or aftermarket option. Where does that other black wire from the small junction box wind up, Blazze? Seems to be heading toward the engine or the front end of the car. Let us know.

As for the strange fuze box slots with no fuzes in them...they are terminals for you to use to power accesories:
BATT - this is a live connection straight to battery power, 12Volts, always hot.
ACC - This is a 12Volt connector that is hot when the key is on, but not hot when the key is off and removed.
IGN - Can't remember specifics, but like ACC its hot when the key is engaged and ignition is fired.
LMPS - used to power extra aftermarket lamps and lighting like fog-lights, etc.

Dude, do not hook any accesories up to these four terminals without asking folks on this website for suggestions and sanity checks. You can easily screw things up very quickly plugging into these terminals erroneously. But when used correctly, they are your friends.