The diaphragm you need is C5AZ-12370-A, Motorcraft DD-190.
true. they do but it is a motorcraft replacement, not autolite which would be correct.
There is no marking on the part, only the box says Motorcraft.
Most of the Mustang vendors (Va. Classic Mustang & NPD) sold the diaphragm at one time. I'd give them a try.
They ran out last year, at least it's not listed anymore.
Jim