Cheers Tony, I guess with every 860 kit being sold, R75 and 80 final drives are becoming more like finding hens teeth... Doesn't look like anyone does new ring and pinion gears from my quick search. So, a S/H final drive teeth count of 32/10 seems perhaps the best outcome, then 37/11 - what is the ratio of the R75 final drive you have Tony? Snowbum mentions R65 came with 32/9 and 31/9 FD's - I think I recall seeing it stamped on the FD before, to find out what I've got?
You mentioned a Siebenrock cam - do they do a 'hotter' cam for the R65? Just asking 'cause I'm kinda curious and amused about that, but it wouldn't be worth the trouble on my old engine either. They should do new ring and pinion gear as well, make a killing! Also while I'm at it, I'm quite impressed by yours and your wifes' combinations of motors in an R65, can an R80 engine fit straight in to the R65 frame and swing arm?