There's at least one guy on here who ran a race this year and wrote about it. Mods that I can think of off hand would be anything to help reduce fatigue... vibe dampening bars and stem, maybe a steering dampener, get your shocks properly set up for your weight and gncc (talk to jogaca). Beyond that, I'm sure some other guys on here will have a few good ideas for you.
2001 Raptor 660: Hot Cams 1, 101mm Wiseco 11:1 piston, 02 transmission update, Prodesign intake, K&N Powerlid, DMC Alien Dual(ish) Exhaust, DJ170/175, 25 pilots, Oversize radiator, Custom grill, YFZ450X Front Shocks, 450 front calipers, Jogaca rebuilt rear shock with KFX700 spring, DG bumper, ProTaper bars, TrailTech Vapor
1988 Warrior 350: 01 660 rear shock, Works DR remotes by Jogaca, DG Xcelerator, Cut plastics
1972 Hustler Amphibious 6x6: Runs!!
1986 Wife: Bone Stock