Brits have no concept of American engines. They would probably say that Abita beer is brewed in Mollington, England. :-)
As good as the IO-540 is... for airplanes... it is surprising to me that someone would consider it to be a good choice for even a “concept motorcycle”. Airplane engines designed for small airplanes are designed to operate in a narrow range of RPMs. Nearly all IO-540 powered airplanes that I am familiar are equipped with variable pitch propellers. I do not think that any of the IO-540s are designed to run at more than 2700 RPM. Motorcycle engines typically are able to be revved up to much higher RPM to get maximum power from their displacement.