Guys have used seats from full size Ram trucks, Lancers, recently a fully adjustable rear bench from a Range Rover - just about anything can be made to fit them (I used seats from a Peugeot 306xsi...) It will require making support rails to adapt your choice of seating but due to the floor pan being relatively flat this isn't a big deal. It will be advantageous to either be able to weld or know someone that can do it for you once you've designed the supports and cut the pieces up to fit. Square tube steel and thick flat stock should be enough. Seats from a Montero would be close and my bet it would only take redrilling the mounting holes in the seat base and adapting Mighty Max factory sliders to get them to go in.