I don't know on the TR8, but an upholstery guy here in town said it is much easier to fit the seats on reverse sides when using Miata seats in a Triumph TR6 or TR4. IE: Passenger seat on drivers drivers side and vice versa. I am considering this conversion on my TR3A. I need a seat with a higher back and head rests would be nice, but in such a low car they may stick up and be ugly.
Jerry