I started work on center-mounting either my 4.5hp CY460 engine or the Tanaka 47R onto a bare frame. It's an NOS steel Diamondback "cruiser-type" made for a 7-speed internal hub w/3/8" axle(135mm). The frame is for v-brakes, but plans are for a Shimano 8-speed hub w/roller brake. So today, I bolted on a universal engine plate and calculated gear ratios and sprockets. They'll range from a First gear of 46.6:1, Second gear of 38.1:1 (both excellent for very steep hills), Seventh gear 17.2 and final drive of 15.2:1.
It's gonna be sweet!