Good morning everyone, In doing a little research, we have discovered that the bumper arm isolators are the same size as the window stop bumpers. The height of this bumper is likely taller(we don't have any new bumper arm isolators to compare with), but these are rubber bumpers that could be shaved to the desired height. These are the correct length to fit the slots in the bumper arms. Here is a link to them: http://www.parts123.com/parts123/dyndetail.pta?acclink=0001018oAACXN
These are definitely taller. I have correct ones I have removed from parts cars if that would help. I would think the early Mustang would be similar.
It is the bumper bracket used on a small bumper car, it is an isolater between the bracket and bumper
Mustangs didn't use a bumper arm isolator. The Mustang window stop bumper is another 1/4" taller than this one.