At the moment I'm studiously avoiding thoughts of 'proper' racing on 4 wheels and sticking to trackdays and now sprints. After a few seasons of club-level bike racing I know how obsessed I get with it and how it can dominate everything. Problem is nothing comes close to racing for excitement! I now run marathons and adventure races instead, tis cheaper and healthier
I guess with it being a relay (6 hours?) it's not so hard on the car as ordinary endurance. When I had my 600 racebike we did a couple of endurance races, 2hr and 4hr. Whilst we had 2/3 riders the bike spent all that time between 10k and 14k rpm apart from fuel stops and a wheel/tyre change in the 4hr. Seemed none the worse for it and is in rude good health still!
Andy