find yourself a morbidelli v8 - modern, powerful - but just a few problems:
- they're rare as hens teeth (and were pricey even when new)
- look like a styro egg package...
but if you're really committed, you could drop your $100k (probable), rip out the motor, and have custom running gear (and a pipe) built for it.
who needs to put a damned chevy motor in a bike just to get a v8.