I just installed an Align power feed on my Bridgeport, and yes there are shims that go there, at least for my Align.
It's tricky to know how many are required without trial and dis-assembly.
I've got some gear mesh noise I'm trying to get rid of, unsuccessfully, so far.
I checked a Servo on a new Bridgeport in the store the other day, and it is smooth and silent when manually turning the handle. Not so on my Align.