The Basslink should come with a wiring diagram for ya. Here's the owners manual:

http://manuals.harman.com/INF/CAR/Ow...sLink%20om.pdf

I think 8 gauge would be plenty for it, could probably get by with 10-12 gauge honestly. I have an MTX Thunderform in my truck with a built in amp and it came with wiring and I think its 10 gauge.