[Jon Jack]

If you want to go beyond the ToughBoxes (which are AndyMark transmissions) that they include in the KoP, then I would recommend buying some of his modification parts. He sells several parts that can be dropped in to make his off the shelf transmissions lighter, faster, slower, etc. It doesn't require too much work to make the modifications either. You can find these parts by going to the transmission or gearbox you're interested in using and then scrolling through the parts at the bottom.