I am pretty sure the aluminum frames come with wider top tubes that are easier to seal and a little more capacity.
It is the same math, just one uses number of teeth and the other use the pulley diameter.Thanks for those pulley size so you swapped the 5'' with a 2.5 pulley. And you put the variable pulley on the clutch or the jackshaft going back to the wheel ( Torque Transmissions ) nice web site has veriable pulley.I'm not shure how to add gear size for pulley's I could figure it out if it was a jeep