Engine wise, it shares the same engine as the Bravo/a I believe. The later 1.8 16v in the Punto/Stilo/Barchetta has a different head (produces more power too). Some parts may be usable between the two though, although I'm pretty sure if the Bravo/Brava engine you would want.
Chassis wise, the Coupe shares the same chassis as the Bravo so no doubt there will be parts that are usable, although I couldn't comment on which ones.
the 1.8 was only available on the continent and never in the UK. Shame really as it could have provided a cheaper way to get into a coupe rather than having to fork out for the stupid insurance premiums the 2.0l engines command.