I assume you have looked at the gp sporting seats, they are very good, winged on both upper and lower bolsters? Gp seat rails have the rear inner bolts going horizontal into what used to be the prop tunnel and the remainder going vertically into the floor so to fit other seats you need a spare rail to engineer, the air bags would need to be compatible too. My understanding is that Alfa seats will fit, certainly there is a thread on here with 147 seats in a mk2 punto including airbags so if they would fit a gp there's a good place to look. I reckon you would do as well to start with gp sporting seats. I am sure other brands would need your insurance informing and that's often a challenge too far.
