I searched some threads on cam chain guides and found some information suggesting that guides for "early" (70 to 73?) bikes are different, possibly due to clearance issues. Online parts sellers like Partzilla, CMSL, and Mike's indicate one guide for all years (not that I trust these sources 100%). However, the parts list I downloaded off biker.net indicates a different guide for just the XS1. Curious what is correct, and if there is a difference, what is the difference?