@lowsinthe20s ,
Hello,
If you have wires from the donner auto's cab, it will be remarkably simpler to use them with your swap. I love the Gen 1 dash but to make my swap simpler, I decided to swap to the donor dash also.
If I had not, it would be far, far more complicated than the simple plug and play. There are several good write ups in the Ranger Tech pages that discuss what you are asking, though not necessarily in the clearest sense.
Regardless of which dash you decide to use, if you have access to complete engine bay and cab wiring harness, that is a VERY good way to start, regardless of how YOU DECIDE to finish.
I am very good with wiring and may rebuild my entire wire harness but not until I've made the donor harness work.
In regards to your light wiring question, he is what I recommend,
Build a stand alone wire harness just for the head lights. I would power it directly from the battery through relay networks grounded to the chasis and controlled from the stock light control switch in the cab.
If you decide to go this route, there are several write ups in the forums and a basic guideline in the Ranger Tech pages. My write up is titled something like "Being Seeing".