Zip ties and duct tape for sure!! JBWeld? Gas and oil... sparkplugs maybe... a spare clutch cable is a good idea, but if you're gonna carry that, a throttle pair would also be a good idea, but then again..I think those should be up to the rider, because if you're gonna carry them on the support vehicle, you'd probably want one for a 350, a 400, a 500, a 550, a 650, a 750...........best everyone should make sure their ride is road ready first, and bring thier own spares...
DEFINITELY map out all the dealers on the way!! If someone does actually need replacement parts someone could go ahead or back for those..Maybe even get some sponsors that way? maybe they'd toss in a free cable or two? or some spark plugs? give 'em a chance to get rid of some of that dusty NOS stuff just taking up shelf space?
... in exchange for a buncha local guys with some outtatowners in for a publicity shot? maybe contact some local news guys for some additional coverage? (maybe even make national news?) local folks could show up on bikes that otherwise wouldn't be making the relay, like 50s and 90s? restored Dreams and SuperHawks? I'm sure some of the local biker hangouts and maybe clubs not necessarily SOHC oriented, but have SOHC members (your local Mods/Rockers or VJMC or..) would also appreciate a little extra attention...gotta lotta time to come up with ideas and get them in motion. So...obviously folks will be dropping in and out along the way, don't want to set a maximum and discourage anyone from participating, but are we gonna set a minimum "group size" per leg?