John,
I could be wrong but I believe Chicago Peotone is probably the third largest show and it's held semi-annually. As for what's after that, there's a bunch of good regional shows; Metro Petro, Dixie-Gas, It's A Gas (Columbia, MO), Roy Reeds, Michigan Gas, and many more but where they fall into size I can't help you.
See you in January,
-Rory