Waytek is about the best out there. TXL is a good grade of insulation for most any project on the car.
For interconnects it depends on what you want to do and where it goes. For sealed connections the Delphi GT150 and GT280 series of connectors is the current popular GM type. WeatherPack is the more popular aftermarket sealed part. For many non-sealed/interior connections the tried-and-true Packard connectors are hard to beat.
Mouser.com is your friend here.
Delphi has a global catalog that has tons of information in it. It's a great resource for everything electrical.
http://www.google.com/url?sa=t&rct=j...FBND-yBZLLksfA
If you're looking for nylon insulated ring terminals the parts sold by Del City are very good but there's usually a 100pc minimum quantity. The translucent nylon insulator works very well and is softer than most others.