breco-flex is one of the best suppliers for these types of treads...they offer a huge variety of belt sizes and types.
as mentioned above you will definately want to run their guided series of belt. these belts come with a self-aligning nub and mate to their own brand of pulleys designed specially for the belt. we skipped their pulleys because of price, and instead got a print from their engineers and machined our own. much cheaper if you have the resources!
they will take a while to get though. our actual belts didn't arrive for about 4.5 weeks. a lifetime during FIRST season. if you have the funds and want to build a drivetrain for 2005 order what you want now.
i know andy baker and the technokats have a ton of experience with belts.....andy gave me another supplier to use last year but i've since forgot their name. maybe he'll chime in with some help.
once you start designing there are plenty of other considerations.......ask about them later if you still want to shell out the cool grand for a full set of treads.
