FIAT 5-6 Speed?

[R6RY D]

Heres a srange one for you, my friend has a 02 plate fiat stillo, its a 1.6 5speed, (with a knackered gearbox) he has seen a a 6 speed from a 1.2 going cheap, i am personally againt the idea , i think the speedo drive will probably be out and the mounts could be different, but i dont know for a fact? any ideas please fellas, ta