Vespa Performance Mods to a Stock Case and Crank
these images are from vespa-ciao.nl. They give you an idea of what you can do by porting the intake and intake window and cutting the crank. enjoy.
more pictures and pages here: http://www.mijnalbum.nl/Foto-AUIOGWGM.jpg
Here is Polini's instructions for cutting the crank, as well as installing it. http://www.polini.com/dep/PI88.pdf