What 5 speed freewheels are compatible with a Sun Rims M13II rear wheel rim? I have a 1972 Schwinn Varsity.  I have purchased new wheel rims. Both the front and rear rims are Sun Rims M13II model rims.   I need to know what 5 speed freewheel will attach to the M13II rear rim hub?   Would the original Schwinn (5 speed Shimano MF-Z012, 14-17-20-24-28) freewheel screw onto the M13II hub?  I can't get the original freewheel off the the original wheel rim, but I would (or buy another one) if I know it will screw onto the new wheel rim.

Thanks!   Nick
Freewheel thread sizes are standardized to an ISO standard which is 1.375" x 24 tpi. See https://www.sheldonbrown.com/freewheels.html. That means any new freewheel you can buy will be compatible with your new rear wheel.

The original Schwinn freewheel might have a different thread (I'm sure others will correct me on this if I'm wrong), but if you are replacing the wheels it's a good idea to replace the freehub too.