if you wanted to do a GNCC type race...there is a group a guys that run in Pa (Kaska, Pa). The race is called the Kaskadilla. Made up of a bunch of local guys and some pro's (Jarrod Mcclure, Chris Borich, Thor Markus, Wes Stone). 99% to 100% of them run 450s, I saw 1 300ex in the video.They've only ran this race twice (kaskadilla 1.0 and 1.5). The next time is suppose to be in Sept (no exact date given). The "track" is Jarrod Mcclure's training track (yes he has raced the past two times-it's pretty much his race). Chris Borich raced the first time they held this event. Unsanctioned, etc. Pretty much, you show up, and you ride. I believe 1 lap is 5+ miles. Race has 2 groups, pro (and those that want to run with them) and the rest.
if you search kaskadilla on youtube, you'll see.
this is trails race, not MX (coal and woods).
I plan to run a Blaster in the next race they have, if it doesn't conflict with my plans to see the Alabama/Arkansas game.