I recently did a restoration of my '59 heater. It's not the same as yours but the squirrel cage design is probably similar.
The silver hub on mine was a tight fit onto the motor shaft. I was robbing the motor from my '58 parts truck heater and used a screwdriver to pry up on the bottom all the way around it's diameter. I broke the '59s hub from the cage (It was riveted on) but was succesful in removing the '58s cage without incident.
truckandcardshop has replacement squirrel cages for $25. You might can rivet or screw your hub back on though.
Jerry
