Why exactly do you want to fit a passenger airbag?
i used to work in the airbag industry and it is not something I would attempt.
I presume you already have a driver airbag. The driver airbag is far more important than the passenger airbag as it protects you from injuring your chest and/or face against the steering wheel. On the passenger side there is no steering wheel so, providing the passenger is wearing a seat belt, the prescence of an airbag is not so crucial.
It just seams a lot of trouble to go to in order to gain a minimal benefit. Also, if I recall correctly the complete fascia is different on cars with a passenger airbag.
midbloke