Look on how the seat belt attaches to the back seat on your car. Follow the way it was done. Generally it's a bolt and two washers. Grade 8 bolt by the way, this is your life.
Actually I have now decided GET racing seats, its final!
Now its which to choose!! Its either the Forzas, TRS's, A4 or LEGACY seats. The Forzas are the cheapest and the rest are basically within 50 bucks of each other.....PICK EM! LOL
Personally the grey TRS's are nice and the Legacy 2 tone are sweet.
I'd go with Legacy. But: I'd just be concerned about them actually fitting in the car. With my CR1s the shoulder support rubbed against the door until I beat it into submission. The Legacy is wider and has a taller support than the CR1. It might not even fit.