Hypothetical:
Your JDM yo SR, ZZ, zxy whatever has a forged crank and my USDM acme doesn't. Why can't I upgrade to a like weighted forged crank for mine, and forged rods too? In the name of keeping costs down by not having to build a new motor everytime mine grenades, because of a cast crank.
Remember some manufacturers have a whizzbang JDM-yo engine, some don't. Is it fair than the Honda, Nissan, and Toyota guys can go to Japan and get a motor but the BMW guys can't?
Or what about the Cosworth engine that came in the Euro whatever?