Will an auto tranny that bolts up to 12a also bolt up to a 13b? TIA Cheers, Dave

 

Yes. Basically, all rotarys share the same bellhousing pattern. You can bolt a transmission from say, an RX-4 to a 2nd gen RX-7. The only trick is that the flywheel, clutch stuff and starter generally needs to be matched to the transmission.

You'll need to check the length of the 12A automatic compared to the 13B automatic.