You want to play around with this site
http://www.368s.com/tools_rpm.phtml
to get an idea how rear tire size, differential ratio, gear ratio etc... effect engine speed. What rpm range does your cam "work in"? You probably want to ask your engine builder what cruising rpm your engine will like. You don't want to be lugging the engine...
It took me a long time to decide on a TKO 600 with 0.64 OD.. Still not sure I made the right choice
