Hi Ian -
The pics below show how we mounted the camera on Roy's 40. The mount was a 'chopped' cheap (<£7) plastic mini tripod I picked up and it was just secured with a single bolt - through the seatbelt anchor bar.
Vibration was not a problem + the camera had an image stabiliser built in too - although I don't think it needed it. I would recommend using a mini Dv recorder if possible. You can pick em up for about £150 now - or you could try a solid-state DV recorder of some sort. Technology moves so fast it's difficult to keep up with it.
You might want to put a 'strap' around the camera to the mount when you do compete and always get permission from 'clerk of course' beforehand, as they get mighty pi$$ed off if cameras appear in cars without their permission....
To give you a taster of Gurston -
http://www.gtd40club.co.uk/videos/Gurston%202003.wmv
Have fun....