I will comment that you won't cruise at 37mph @ 3600 rpm, the engine won't pull it. You want the rpm to be a little higher (more reduction) like around 6-7000 at 35 mph.

Your project is very do-able, with a few slight changes.
You can weld a sprocket to your present clutch, just be carefull not to warp it.

Others here with more knowledge on the DIY bike subject will weigh in here shortly.

Welcome to the forum!

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