Hey all i'm having trouble identifying this gearbox, came with a car i brought that had a 12a in it, my 13b doesn't fit flywheels to big (320mm) also looks like a 300mm won't even fit. All bolt holes line up though.

 

looks like a 2gen na 86 maybe

 

IIRC, the cross-member and the way it mounts looks different from an FC. It's possible the cross-member was swapped / altered, but I think the way the cross-member mounts to the FC transmission is by mounting the Y-piece flat against the bottom of the casting, and then the cross-member bolting to the Y-piece. In your picture, the Y-piece mounts to the transmission on it's ears instead of flat on the bottom. The shifter on the FC is also straight up, whereas yours looks angled.

I also haven't seen the Mazda logo cast into an FC transmission, but I also have no experience with the S5 parts.

I know that you're in New Zealand so there may be some variation in the options that cars got, but I'm guessing that if your transmission isn't an SA/FB piece, it's from an earlier rotary engine. Only a guess though.