Link?
Nm I got it. The one big advantage of the B5 as far as I can tell is it has clear universal mounting points for the side brackets built in to the seats (you will still need a bottom bracket to mount to the floor like a PLANTED for example and those are HEAVY! unless you make your own weight reduced version) plus of course FIA homologated which NHRA does not care about. But I don't know if this is worth another $800 or so. Here's a great deal on side mount brackets, I never knew these existed until today:
Buy InVictus Steel Side Mount Brakcet for Bucket Race Seat (1 Pack, Black): Seat Brackets - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
I don't know why the other seats don't have any visible provision for mounting - elise spares told me you have to DIY that part.
So to your original question of how to mount this type of seat, here is a pic courtesy of Invictus
The side brackets can mount straight onto a floor cracket or if you wanted an adjustable seat you would put the side brackets onto a pair of sliders and then onto the floor bracket.
This would be the sliders:
Buy Invictus Universal Vehicle Seat Slider Track Set for Aftermarket Seats (Pack of 2): Seat Brackets - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
And this would be an example of floor bracket
The Planted Seat Bracket is a vehicle specific bracket used as an adapter between the floor of the vehicle and an aftermarket seat and it's accessories. Because the floor of each vehicle varies and typically is not flat, a vehicle specific Seat Bracket is required for installing an aftermarket seat.
midshipgarage.com
By now you are getting the idea that cost - and WEIGHT! - add up fast on these items. But still gonna be a big weight savings over OEM.