I have heard of this being done on TY's, putting a 250 top on a 350 case, although I never had a clear understanding of the benefits. Something to do with larger flywheel/smaller piston = more grip?????? In this case, simply buying a 200 would not give the benefit, right?
What is the theory?
BTW, you should be able to buy a 200 top end kit from RYP that will bolt on directly.