Well here is my first oil sample from a car I am racing with the SCCA. The previous owner had run Mobil 1 5w20 in the motor since that's what is spec'd on the cap. The car is stock except for a cold air intake and tune to run on 100 octane street legal fuel (unleaded). The previous owner mentioned that he cut race fuel with pump gas (93 octane) to reach 100 octane but didn't say it was leaded. Based on what I'm seeing here I would call it a safe assumption to assume the fuel was in fact leaded. I have reached out to the previous owner to confirm.
I'm estimating the usage to be around 700-1000 miles in race conditions only but can't know that for sure. I've spoken with a lot of people and there is a pretty even split on running 30wt vs 20wt since the motor is stock. I run in the Touring 4 class which really restricts horsepower so any little bit makes a difference.
I'm currently running Redline 30wt Race Oil with a M1 filter. I will get an oil sample from it when I change out but may go back down to 20wt for the Runoffs to get every last hp out of the motor.