odyssey cylinder conversion

[Air-cooled-R]

I'm working on another airfooler for the summer and I'm wanting to go bigger. I've been reading up on putting an fl350 odyssey cylinder and head onto a 250r base. I'm understanding that the cases have to be machined and the cylinder cut or the crank stroked. Can anyone tell me if there is a company that does such a thing and approx. how much it would be, as well as any more helpful tidbits of info? thanks everybody.