As for the airbag pyro for the seatbelts, The airbags WILL go off even if they arent connected. The problem is you need them connected to reset the airbag controller.

I had mine out for about.. 6 months.. after rolling, I had to contact the person I gave my factory seats to and have them mail back those parts ( or buy new ones, its almost 500$ for the both of them ) for the new airbags.