The PAX Index
The PAX Index is a system of handicapping cars, so that cars in different SCCA classes may compare times against each other. John Kelly tells us it was invented by Jim McKamey for a series of autocrosses he ran at one time, and is now updated each year.
The PAX index for the fastest class (AM) is always 1.0. For any other class, multiply your time by the index for your class to get the time you theoretically would have run in an AM car.
PAX numbers are compiled primarily from the results of a series of midwestern events, though some attention is paid to the Solo II nationals.
Sacramento Solo2 page