Put "MX5" in the Search Box and look in the other thread called "Seats" and you will see pictures of the seat in place and a drawing of the adaptor brackets I made to fit the seats to the original GT seat rails. The Mita rails my be newer and even better but using the GT seat rails means no new holes in the GT floor pan and a direct bolt in/take out job that requires no modifications to the GT.
All this plus neat wee radio speakers in the seat back!
Score the speakers from the MX5 doors too, if you can, then you have a good speaker system for the GT as the Mita door speakers can go behind the seats in the parcel shelf or where ever you want. This provides a balanced speaker system but I don't think the original GT radio can drive all these speakers without a new amplifier unit in the scheme of things.