It would be completely pointless to build a "WRC" engine unless you are tied to the restrictions imposed by WRC regulations.

Build an engine suited to your needs, not a specific race series. WRC cars run a tiny 30 or 32mm restrictor before the turbo, so their engineering requires very specific design that no normal engine would ever want to use. Because of the restrictor they operate over a much smaller rpm range as the engine is strangled.

So are you tied by those rules ?