1. Castle nut and drum puller was used on 8.75 axles up through 64 which was not used on the 7.25 axle
2. Which is what You have. Do what the previous poster said and it might pop off. If not, chances are the drum has a ridge on the outer part where the shoes make contact. If so, you’ll need to adjust (from the rear) the shoes so they’ll be able to clear the ridge on the drum.
3. It might have been swapped during the 50 plus years since the car was assembled, but the chances that it’s original to the car are quite good.
