All but impossible. The Brotherwood conversions carve a huge (and impressive) channel into the floor to allow headroom for a wheelchair user to get the the front of the car via the tailgate. Not only do all of the rear seat mountings get binned, but so does most of the floor that they would bolt to. One of the rear seats that is retained is mounted on special frame that’s side-mounted to the body. It folds and tips sideways to let the wheelchair pass.
It’s worth having a look at listings for them on eBay as the photos usually give an idea of what’s been done. It looks like a lot of work. The distance that they drop the floor has to be seen to be believed. They would make a fantastic motorcycle transporter for anyone in a lower level racing series on a tight budget and without the space to keep a van