You need to decide, if you don't already know, what stock stuff needs to work and what doesn't. If this is to be a street legal car, then I'd consider using a stock wiring loom if a good condition one is available. Get all of the electrical components mounted b4 you start wiring things. It makes it much easier if you have fixed 'targets' to pull wire to than if such-and-so part is going to be 'over there somewhere'.
If you're going to start from scratch I highly recommend you buy one of the hot rod books on wiring and completely read it b4 you cut the first wire. Check for these two titles: "Automotive Electrical Handbook" by Jim Horner, or "Tex Smith's How to do Electrical Systems" by Skip Readio.
BTW, VW electrical fuel gauges use a calibrated resistence wire from the sender to the gauge. Don't know what the resistence value is. Replace it with a normal wire and the gauge will read wrong.
6 volt or 12 volt car ? Recommend you toss everything 6 volt if it is a 6 volt car except the starter. It will work fine on 12 volts. If you can get your hands on an Autostick starter, then I'd toss the 6 volt starter as well.
Wiring supplies: Delcity.com, Westmarine.com
Buy a quality wire crimper, you'll be using it a lot if you elect to start from scratch. Channelock makes a nice one.
"It only seems kinky the first time"
-- Bumpersticker seen in Lost Wages