They are easy to remove if you lift the arm to the full up position, and pull the small tab along side of the base, out. It locks the arm in the up position, and a couple of quick wiggles will have it off. There aren't any cars that I know of with a similar arm. There is a company that makes similar arms, but I lost the URL.
I do not have one right now. Check with Buicknutt. He has a number of donor cars.