if you have a petrol multipla it must be the 1581cc 16v engine.
yes you can take a gearbox from any 1.6 bravo, brava or marea regardless of age. i'm not 100% sure if the 1.6 stilo uses the same box, but i'd be very surprised if it does not because it uses the same 1581cc engine. any fiat group vehicle using the 1581cc engine should be a suitable donor.