Well ive got it all ready to install now and have been reading up on my most hated area, wiring and elecrics.

Cant be too hard, 5 wires and i know what they are for, and read the wiring diagram for the car.
I tend to over research these things.

I just want to confirm before i butcher it, i was just oging to splice the harness into the rear of the cars plastic pug (use probes to push the wires into the back of the factory plug harness).

on the tow harness white equals ground in the center, green = right turn, brown = tail light , red = running lights and yellow = left turn.

I understand yellow and green can be wrong way round just need to test with test lights.

on the datsun wiring diagram:

GBL (green blue tracer)= running lights off the rear number plate lights

GR(green red tracer)= left turn indicator
GB(green blue tracer)= Right indicator
GY (green yellow tracer) = brake lights

will make a ground with a self tapper in the boot floor.

so basically i hook harness wires to datsun.

harness wiring = datsun wiring
green = GB
brown = GY
red = GBL
yellow = GR

does this sound correct?

Sounds about right. It would be better if you used proper multi terminal connectors. One it would look like it was part of the rear harness and it makes for more stable connections and if at a later date you remove the towbar you just unplug it.