There's nothing wrong with the V10 in the Gallardo, send it to Underground Racing for a TT build and you will own the quickest car on the streets of planet earth. Just google search 1500hp tt Lambo to see what's possible with a V10.
There is also the VR6 engine configuration.
http://en.wikipedia.org/wiki/VR6_engine
Formula 1 racing engines
http://en.wikipedia.org/wiki/Formula_One_engines