Bought a second dedicated autocross/track day/go nuts car. (Which is now the new plan...) When I got my '74, the original plan was to make it a daily driver and occassional autocrosser. The problems with that are twofold; 1) Daily driver and autocross setups are different, so you're always choosing compromise parts (stiff but not too stiff, loud but not too loud, etc.), and 2) If you break it on the track, there goes the daily driver for some unknown period of time.
Of course, I don't have space and time and money for two cars, but that's a different issue entirely!