I know of guys sending off the crankshafts out of JD As & Bs to be stroked. They weld up the rod journals on the rear side up to 1/2" and then turn them to give more stroke. The downside is they have to remove some of the crankcase casting to allow the rods to clear at BDC. Then they're bored big time, cams reground, governor RPM spun up and secret fuel additives used. I haven't heard of one blowing up yet. There is 5 or 6 in this immediate area.
My family never has believed in modifying anything for more power other than an upgrade in piston designs when time came for a rebuild. Otherwise everything has been kept stock, including the electrical systems. Dad always said he sold enough parts for stock machines that destroyed theirselves by being overloaded. I guess it really depends on how well overbuilt the original machine is. When you look back at our farming history, when a machine was deemed too small to get the job done, it was traded in on a larger machine. Don't get me wrong, not condeming the practice of squeezing out more power--it certainly adds more flavor to a tractor pull!
Is your engine a John Deere or Hercules? Deere used their engines in the later models. I have 3 of the Deeres, mainly for parts.Dave