Will the 4port 5 speed RX8 engine work with my 6 speed transmission?

 

The 5 spd and 6 Spd transmissions have the same bell housing bolt pattern and are the same length, so you can swap the transmissions. You would have the change the disconnects for the neutral and reverse switch. Are you asking about swapping transmissions or putting a 190 hp hp in a car that a 230 motor came out of?