You could probably re-grind the stock cam, but you'd have to get it re-hardened. Then you'd need longer pushrods to compensate for the smaller base circle. Probably need stronger valve springs too.
Finding someone with the machinery small enough to do the job properly, and put the proper surface finish on it would be the hardest part I think.
Don't some of the guys racing YS's get their cams ground, or get "high Perf." cams somewhere? Seems I recall reading about that here somewhere a year or so ago?