Our car was stock port but ran under the CalClub regional only rules for RS (radial sedan) that let us run a carb (48 down weber) at 2,222 lbs w/o driver.
Essentially a lightweight ITS car.
We never ran the motor above 7,500 RPM and stayed on our target lap times.
We did incur two 5 minute fuel penalties as well as a $50 fine for using a water only fire extinguisher in the pits. We did have multiple chemical extinguishers we just took this one over the wall during refueling and got caught with it.
The classing for these enduros seem to be a little screwed up. There were cars that should have been classed higher than us in our class, and cars below us that were very fast.
I suspect that some of the SM cars were less than legal.