The original instruction manual for the 2130 Wards lathes does not specify a motor frame. They only call out speed and hp (1/2 hp). I have a 56 frame motor on mine. If you go with a capacitor start motor, I recommend not picking one with the cap mounted on the top of the motor. Instead, get one that allows you to mount it with the capacitor on the rear of the motor. There isn’t much clearance under the jack shaft for the motor. Mine just fits. It wouldn’t work if it had the capacitor on top.
the other thing to match up is the shaft size to your pulley bore.
There isn’t much benefit to upping the horsepower. The flat belt is meant to slip if things bind up or crash. Any additional horsepower is useless once the resistance gets high enough to slip the belt. You could go with a rubber flat belt and tighten the belt tension to keep that from happening, but I’ve never had an issue with my canvas belt and 1/2 hp motor not getting the job done.