Re: PAE
That is it, and I think you may be right about the early cars not having them, but yours does have the bosses for the rubbers cast into the pinion housing so I'd assume yours should have one fitted. Fitting doesn't necessarily mean you'll cure the vibration you've got, but it will be one more thing eliminated if that turns out to be the case.
I have one if the ones you're looking at dont work out.