My 2 cents.... Doing it through the primary can be a difficult job. I would change the rear wheel sprocket (pulley) and get a longer drive belt. The 6th speed light will still work but the speedo will read faster than you are really going. For that problem you can buy an electronic "black box" which allows you to tune in the correct VSS frequency and get the speedo to read correctly once again.
I have seen aftermarket crankshaft primary pulleys with fewer teeth. It eliminates the factory compensator for their own 'power absorbing' invention. That can be the kiss of death for a press fitted crankshaft like you have. I wouldn't do it.
I think Baker has the sprocket & belt available as a package.