Yokomo MR-4BC help!@!£!

[chokoboy]

Hi!
Im fixing up my old yokomo mr-4bc 2003 special version and need some help. Im going to replace my 84t spurgear but im not sure what the part nr is, i found one 84t zs-s84, zm-s84 & sg-4884 anybody knows the difference between these? And wich one is the original for the 2003 special version? Does anybody know where i can get parts for the mr-4bc?
Thanks alot