the 4mill is the way to go. then, if youve gotta have a big bore, just get a cub. lets say the vitos bb kit is 500 plus about 4-500 in porting. thats $1k. a ported cub is around 1100-1200.
and before anybody says that he may not want all topend power like a cub, note that he has 34pjs wants cpi's and wants around 75hp.