it would not be difficult to run this as a 3 event competition with multiple cars
all you have to do is work out a points system for the 3 types of events... autocross will be the hardest to do a points system for...
3 events, 100 possible points per event, 300 total points possible, higest points wins
drag racing
10 seconds is a good place to start from
every 10th of a second over 10 seconds drops a point off
10.0sec = 100pts, 10.1 = 99.....20.0sec = 0pts
limerock
the track record is 43.112 seconds... not that anyone is at any risk of getting that or even close to it but its a good place to start
every 1/2 second over 43.0 drops a point
43.0= 100pts, 43.5 = 99..... 93seconds = 0pts
autocross
now this will be a bit trickier due to the fact that the course will not be known untill the day of the event and the best time for that course will not be known untill the end of the day... so for autocross it will be the FTD (fastest time of the day) for 100pts and one point will be lost for very 0.05 over FTD... that gives you points for anything within 5 seconds of the FTD...
so if the FTD is 48 seconds that will be 100pts 48.05 = 99.... 53.0 = 0pts
the only problem would be if none of you come within 5 seconds of FTD... i guess it could go by 0.1 to give you guys 10 seconds over FTD (if you cant land there you should not be in a competition in the first place)
so while this does not give a true "best of 3" it does give an overall best car/driver... the only thing that would need to be worked out is a tie breaker in the event of 2 drivers getting the same overall score after the 3 events