Fair enough. I'll tell you a little about what I want to do.
I'm 62. Been riding all my life. I've ridden to all the States and Canadian Provinces that you can get to by road. Two years ago I had a stroke and can't ride a bike (or walk). I want a way to get around our small town. Never be more than two miles from home, and do't need to cruise above 35 mph. I can weld, bolt stuff, etc., but have no access to large machine tools.
Besides being cheap, I'm deaf. That is more of a problem than you would think. You can't hear the motor rev while using a clutch. Real PIA!
I started out intending to buy a 250cc auto scooter and build a sidecar. I have two sidecars so I understand the dynamics.
Then I thought of that old ATV. It has no clutch, you just shift it. I also have an old Moto Guzzi rolling chassis and a extra light weight sidecar frame. The idea is to shoehorn that motor and transmission into the old Guzzi frame and add the sidecar to provide stability and also have a way to carry my manual wheelchair. But, that driveshaft is a problem.
The Guzzi is shaft drive, but the drive is on the wrong side. What I would like to do is remove the shaft and go to a chain drive. Changing the rear wheel will require some thought, but I can make that work.