I just did the 16 tooth install. I got the sprocket from Sprocket Specialties out of Oroville. The price on their website is old, as the price is just over $20.00. I also got the 39 tooth rear, but didn't install it yet. I LOVE the new gearing. It works well with my Yoshi full titanium system and dynojet jet kit. Maybe now I can keep up with my pals on their KTM's and their Aprillia's.
The install took about 45 minutes. Only a little grinding on the case saver and a little notching on the rubber grommet for gear clearance. Now 75 is just cruising instead of screaming.