Well the stock crank in my 350 was apparently handling 300hp for 20 years in a boat so I would have thought that envelope can be pushed a fair bit.
According to that Jim Richardson fellow the stock cast crank if its balanced along with the rest of the rotating assembly will happily handle pretty much whatever you can throw at it normally aspirated.
Scat stroker cranks are peanuts though, so why bother with the stock one ?
RPM Machine - Product » 1-91050-1 Chevy 350 to a 383 Stroker Kit...