ill tell you this about the 929, it has a horrible aftermarket. And i the only forum i ever found on them was at mazda world...lol i like thos cars alot. And i was lookin into a 13B swap into one for awhile and still am. but if your gonna mod that car your pretty much on your own as far as mods. And the jspec version of that car "LUCE" was pretty popular in japan, it came with a 13Bt, but as far as that 3.0 motor and mods i never seen anything but a filter adapter. but i have found the J30T 3.0 turbo v6 swap isnt too much trouble, and the motor runs pretty cheap on Corksport.
what year u got sohc or dohc? i have a thing for those cars.. especially the 90-95's!