Hi there, I've been using the below as a ballpark gearing guide for my cougar:
http://www.teamnovak.com/tech_info/b...r_gearing.html
With a 10.5t motor that would mean a 26t pinion with your 80t spur to give a FDR of 8.0 if you haven't changed the internal gearing from standard. I'm no genius though so I'm sure someone has a better suggestion
