Pete,
Tamiya makes (or did make) three different bevel drive Dukes:
The Mike Hailwood Replica, The 900SS, and the 900NCR racer, all based on the same 900cc bevel drive Desmo engine.
The 750ss can be made from the 900 kit (much as a 748 can be made from the 916 kit)- but you'll have to get some custom decals made for the side covers.
Many years ago I built a 1/9 scale (I think!) bevel drive Ducati 750 Sport - the kit was by Protar - fairly well detailed but not REALLY well detailed (if you know what I mean) - took a lot of work to make a beautiful model from it. It may still be available - maybe check Ebay. Good luck.
Cheers
LeeTree