I had this problem on my original 88GT. My passenger side front caliper was sticking and that wheel would still
be braking.( brake fluid wasn't fully coming back to the reservoir) I changed the rubber brake line hose and that fixed the problem.
This car was stored since 1995 until 2010. Its was driven a few times when it was stored.
I didn't check for a clogged brake hose, but from a 40+ experience mechanic told me he seen it happen exactly where
you mentioning...at the metal mounting tab on the UCA. It can rust and clog at that spot.
At the same time, I replaced both front brake hoses with a Raybestos brand brake hose.
Thanks for sharing your experience...its never a bad question to ask.