After figuring out the correct routing of the wiring loom I've discovered a short that burnt out some wiring.

The short occured in the front trunk where the driver's side headlight & motor loom t-off the main loom. Likely something in the front damaged the wire and it shorted on the body causing the damage.

The damaged wires (on the driver's side light loom) are as follows;

Grey with black stripe
Plain grey
Black with white stripe
Green with black stripe
Plain white
Plain yellow
Plain red

4 brown earth's

Can someone advise me what these wires are and what the correct gauge wire in modern wire I need to buy?

It's a 1974 2.0 model.

A bit of investigation and i think i have the correct modern thin wall type of wire to replace the damaged bits on the loom.

Can someone check the list below and advise as to whether i have this correct? My weakest skill is electrics and my manual does not have usa 1974 wiring diagram. I've calculated the ratings below based on fuse rating on the circuit and the original wire thickness, be they thick or thin.

Head lamp motor has 3 colours;

Thick red, i would replace with 16.5 amp 1.00 mm thin wall pvc cable
Green with black stripe, i would replace with 11 amp 0.5 mm thin wall pvc cable
Plain grey, i would replace with 11 amp 0.5 mm thin wall pvc cable

The head lamp has 3 colours;

Plain white, i would replace with 16.5 amp 1.00 mm thin wall pvc cable
Plain yellow, would replace with 16.5 amp 1.00 mm thin wall pvc cable
Brown earth, i would replace with 16.5 amp 1.00 mm thin wall pvc cable

The remaining wires being;
Grey with black stripe, i would replace with 11 amp 0.5 mm thin wall pvc cable (parking light)
Black with white stripe, i would replace with 11 amp 0.5 mm thin wall pvc cable
(turn signal)

The earths i would replace with 16.5 amp 1.00 mm thin wall pvc cable.

more than you want to know.
In color too.
pelican wiring diagram
Carlos

Is there a source where one can purchase automotive wire with tracers to keep the harness original looking?

Go to the WTB section and get those sections of wire from the right year car,solder and heatshink all the joins you will be good.
Make sure you know what caused the original short circuit before going any further however.