You might want to consider the RX8 5 speed box for your application as it has longer legs than the 6 speed. First is often cited as too low geared on the 6 speed to be of any use anywhere but climbing the North face of the Eiger, while fifth in the five speed is a significantly taller ratio than sixth in the 6 speeder meaning less revs at high speed.
https://www.rx8club.com/rx-8-discuss...-promise-1660/
5 speed tends to be cheaper, too.