This is a picture of the interior of a 1999 Miata. Are the seats for this and an FD the same? They look very similar.

 

No. The Miata's are a little taller and more narrow with no hole between the seat and headrest.
Plus, there's no clip/hanger for the seatbelts on Miata seats and the FD ones sit lower to the floor. I can get my arm under my Miata's sets, but not the FD's.

 

I know Mazda went to a lot of trouble to keep the weight down on the FD's seats so I'd bet they're lighter than the Miata's too.