About two weeks ago, I was watching the Colorado Hill Climb Association running on a track here locally, and after watching one session, I'd have to say you need three more oil filters, a stack of air filters and change the oil after each run to keep the adobe out of yer engine . .
Those Bearings are looking pretty good for a car exposed to that kind of environment for any length of time!
Back in the mid '70s a buddy of mine and I had a Volks single seater with a 2180 in it, and while most of the tracks were no where as dirty as the one I was at the other day, we changed oil and filters after every race. Not "Event" but every race, and still had some pretty worn and pitted bearings on a teardown. And with Volkswagens, you took 'em apart pretty frequently. If you didn't then they'd do it on their own, often without warning.
If you got it to live that long, keep doing what you're doing . .