personally, for a trail bike, i would just send your stock cyl in for some work. you can get decent power out of them if you do the whole setup with domes to match and everything. if you want more power that a 350 can support, do a 4 or 10 mil or something like that. i know that is getting into more money, but then, if you decide to upgrade later to a cub or something, you already have a solid bottom in. just my opinion of course.