the supercharged V6 is already in toyota's road cars and emission tested etc etc. would be a piece of cake to slot it in
same, i haven't been keeping track but i'm sure honda has some similarily good V6's. some people have converted their elises to K20's and the results are impressive, even if i can't see it being worth it lol.
at the end of the day, at least you know servicing costs and parts shouldn't be too bad