With regard to the twin plate setup I recommend only using the organic linings for your application. Avoid cerametalic and sintered plates for your application Rob.
As Mark has mentioned you will need to do some R&D to get this spot on for your application. I am in the process of developing a twin plate 7 1/4 kit at a competitive price for FWD applications but sadly the R&D is not finished so I can't offer the kit to you at the moment.
I also agree with Mark that the B5 simply cannot cope beyond 350bhp. Oli's cvh powered car is now at 350bhp and the gearbox last a VERY limited amount of time!