I have found out the hard way that not all bottom mounted Recaros are the same.
Just keep in mind that when you are swapping seats and have the OEM rails, you can only swap in flat bottomed Recaro seats such as the LX series and SR (up to SR-5). Some later models such as Speed, Trendline and Sportline have an entirely different bottom which is made from a plastic shell as opposed to the old design which uses a rubber diaphragm. The plastic shell design protrudes from the bottom of the seat and the OEM rails do not have enough clearance to bolt up, nor does the bolt pattern match.
Old design:

New design:
Luckily Recaro Japan makes rails for the MR2 that fits these newer seats but they cost a pretty penny. The part numbers are 2080.142.1 2080.142.2 for left and right respectively. I'm currently sourcing these base frames from Idealseat in Mordialloc.
In conclusion, if you want to use the OEM MR2 rails, you will have to stick to the older Recaro design. To this end, these types of seats were shipped as factory standard in cars as late as Evo VIII and DC5 Integra.