What first
I like to pre make my harness and leave extra length and loop it.
you can always come back and rewire later. in my experience when you are swapping you will probably have to change stuff around anyways.
If you are going to re-wire the whole car, get the wire in place now. However, before you can do the whole car completely, all of the hard components need to be in place, before you can run the wiring. All of your components need to be in place, otherwise you will be doing **** over and over again, which is a pain and can get expensive.
Andrew
This is of course 100% theoretical and based purely on hindsight from having done the opposite of what I said.










