twm doesn't build a shifter for the rx7. your options are a corksport shifter, a modified miata shifter, a short shifter from mazdatrix.com, or a mazdaspeed shifter.
you can't really go wrong. i would recommend the shifter from corksport.com. they are extensive with their testing and development. it took them around a year to come out with their short shifter for the FC because one of their shifters from a totally different car broke during beta testing. they took that as a chance to improve rather than just put out a product that may or may not be solid.