We would recommend contacting a transmission manufacturer for correct transmission.
Make sure to use the proper flexplate or flywheel balance per each engine's balancing. Engine balance, converter speed, and other recommendations can be found under each engine's specific part number on our website.
If you're looking for a new transmission we would recommend Gearstar or Bowler Transmissions for Automatics, Tremec for manuals.
We also offer engine/transmission packages if you're looking to upgrade your transmission: