Sorry, just seen this post. @Sev I have the gearbox from a 748 but to be honest the bike revs really quick and goes through the gearbox fast, so I didn't change it. I did however put an ST2 gearbox in. The original gearbox was toast, worn. I broke an ST and took the barrels, camshafts, and gearbox for my SS.
This one any good? https://www.ebay.co.uk/itm/39413780...DsyS5v5QaO&var=&widget_ver=artemis&media=COPY