Tranny bolt pattern
 

Will the tranny used with a 85 12a fit any other Mazda motors?

RE: Tranny bolt pattern
 

You can change the center section, using the rx bell housing and rear section and use a early miata gear set. bell housing is pretty much rx only but hopefully you dont have any cracks or dents.

Just one note, the input shaft needs to be shortened about 1/2 inch to fit into the eccenter shaft end, that is done very easily. have fun with those nice tight miata ratio's!