I had one on my early Plainfield years ago and can't remember why I removed it or what I did with it. There is a special tool to remove the carbine rear site or if you wish to get after it with a hammer, it comes off from the left to the right looking from the rear. Some are staked on so you may have to use the tool, also available from fulton armory.
If you have a Universal or late Plainfield I'm not sure what will or won't fit, those are unique to say the least. Some Universals came drilled and tapped for scopes.