Not an orange box.
Did backfire and fried part of the engine harness by the carb
There's the clue. Look at which wires got fried.
Wires that overheated internally did so because of too much current through them - usually due to short.
In other words one of the conductors or something it was connected to touched another wire or ground.
IIRC '73 begins the electric assisted choke, so that is one possibility, but go by what the wires show, not some guess from a guy who can't see what you see on the car.
