Mick,
The wiring under the dash on my car was in sad shape due to a fire, rat damage, and some poor repairs by a prior owner(s). Being there was nothing rare about the car, I built a new panel as you are doing.
For connectors, I used trailer wiring connectors so that I could easily unplug or replug if I needed to pull the dash-for instance, I took the two turn signal bulbs that I installed and took the hot side from each and ran them to a two pin connector. I took original two turn signal wires, cut them off and attached the left to one side of the mating trailer connector and the right to the other side of the same connector...making sure they matched up with left and right in my new cluster.
I used leds for all bulbs for hopefully long life and because the dimmer is burned out in my light switch.
I did the same with the common ground wire of the cluster and the ignition hot wire of the cluster. I used mechanical gauges for the cluster but I put in three jewel lights for Brights, E brake, and, a oil pressure warning light (in case I ever get around to teeing a warning light sender into the oil pressure feed).
Given the wiring was in such bad shape under the dash, I clipped off all the bad leads that went to the dash and replaced what I needed or rerouted an individual wire if I did not like how it was done originally. I by-passed the bulk head connector with several wires due to bad voltage drop from undersized/corroded/burned contacts.
In other words, I pretended I was wiring a hot rod.
