Randy,
this is the starter that I used; it is 3 hp not 3.5, so no burgers for lunch, before backing up.
https://www.ebay.ca/itm/SBC-BBC-CHEVY-3 ... dF&vxp=mtrThe bendix gear is 1.165" OD, and 9 teeth.
Here is a good candidate for a ring gear. Don't know the diameter, but it looks about right. Check with the vendor. The center can be machined off, and a mounting plate made to be sandwiched between the flange and the u-joint.
https://www.ebay.ca/itm/Yamaha-Snowmobi ... Ui&vxp=mtrI had thought about a soft start, but couldn't find something suitable. Don't know if that would make it more user friendly; it is not the most elegant drive system to begin with, however, it works just fine as it is. My daughters would rather that I don't back up; it sounds too embarrassing, Dad
I find, that with the roll cage, it is just as easy to push the car back. I only use the reverse when I'm already strapped in or in an emergency.