Low, before I start the build or thread, let me ask your advice as you just completed a very similar build
I do not have a threaded wheel like yours, my wheel just has a standoff where the three bolts hold the #25 sprocket onto it. Monsterscooterparts sells a similar trans with a #25 sprocket on it which is also 5:1 ratio
http://www.monsterscooterparts.com/trfor3336434.html
I do not see a easy or cheap way of going with #41 or #35 chain without having a freewheel like your back wheel.... trying to do this on the cheap here
Going this way, the gearing will not work, 5:1 reduction with a 20 feeding the 55 wheel gives me 13mph at 6,000 rpm's. I do not want this for speed at all, but she would be wound out at 13mph screaming
Any ideas or leads to better gearing?? I can not find any other 3 hole #25 sprockets online