The old Fiat twinc was a fantastic engine, tough as they come and very tunable. Fiat gearboxes are made of chocolate though so don't go near one (I had one explode at 80MPH and it was scary in big brown sloppy dollops
). don't know if there are too many of these lumps around now as they are really old tech by modern standards, not sure quite when Fiat dropped the twinc ut they were certainly in production into the eighties.
D.
In edit: sh!t, I just realised that makes them at best 21 years old and at worst 30+! I'm getting old :-(