There are a number of good wiring harnesses out there. Just be sure you order the unit that has the number of circuits you need plus a couple more spare for additions down the road.
As far as connectors are concerned, a lot of guys use StaCon type connectors. These are the type that get crimped. I always use a crimper with a 'tooth' for a really good crimp. I have read were soldered connectors in autos should be avoided due to vibration. I personnely have soldered many connections in steetrods. I'm working on a Lincoln Zephyr right now and it uses Ford connectors which are soldered so who knows.

Six volt guy living in a twelve volt world