You will need to buy a new dash board with this encased.
barchettaparts.com
Then you will need the relevant modules, the ECU may also need to be re-programmed, but logic would suggest both airbags would deploy with the seat belts incase of an accident.
However everyone who knows Barchetta's well will know which age car should and should not have airbags, 1st question I would ask "Have the airbags gone off as they have been replaced"
I agree it would be a great idea to fit them, but it could be more hastle \ cost than it's worth.