I am running a 14 x 6 on my 91 fx and it did great on my 60 size stick. I mean it would haul freight. Not long ago I stuck the engine on my Revolver 70" but does not quite perfom as good. It acts real sluggish. I plan on dropping down to a 13 x 8 or 13 x 7 and give that a go to see what happens.

It is amazing how taking an engine from one plane to another changes everything. The whole setup needs to perform well together.