I do not think the mountain road pictured earlier was as bad as you insist (certainly there are patches of the 101 which I would be more careful on), an XK120 has only half an inch more ground clearance than a GT3RS. Also I still maintain that a gravel trap or high curb poses more of a threat to your GT3RS than a country road. "If you've never been off track in your racing career, you're not pushing hard enough." Plenty of tire walls and plenty of hay bales have welcomed GT3s and XKs driven to the edge (by much better drivers than you or I).
Of course there is a difference between a track day and really, truly racing.
Even, I suppose, the gentleman's sort of "racing" done now in vintage machines. I will still do a cross country rally, and not all of the roads are track smooth (or even properly paved).
Cheers