A lot of Mk1 MC18 (R2/4J) stuff will work with an MC16 Barry, as Paul's already said. Crankcases for the MC16 are unique however, as the engine is solidly mounted, unlike the later models.
MC16 pistons do actually differ to the other models, but not in any detrimental way, and any piston/rings from any NSR (including MC28) are a direct fit.
Good bodywork is the real pain to find, as are CDI packs, but pretty much anything else can be found floating around the usual places.
_________________
Andy.
NSR-WORLD.COM
Please keep all responses to Forum posts on the Forum so that others may benefit.
Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.
Check us out on Facebook! Please "like" our page!