It looks like new wheels with freewheel hubs are available, which surprised me: https://carsoncitybikeshop.com/wheel...rim-freewheel/

Many are nutted, but that one's QR. But it is 135mm wide so cold-setting the frame will probably be needed. It's probably at 126 now, and the QR might slip if not properly cold-set.

Long reach brakes will result in slightly less braking torque. You might need good pads, like Kool Stop Salmon.

I'm not sure what crank-crunch is, or how a rear wheel could cause it.