Failure-brake proportioning valve vs.master cylinder

[Alexander, Tyson]

Oh Great and Powerful List,

The short question:
86 4kcsq- 180k miles- Which is more likely to go first, the brake
proportioning valve or the master cylinder.

The long description:
Car sat for a year. I performed the necessary prep to get it started, let it
run awhile, and started out of the driveway. When I tried to brake, pedal
went low very softly, front right side shuddered horribly. I examined, and
found that both front inner pads were worn very near the backing plate. I
replaced the pads, withdrew, cleaned, and lubed guide pins, cleaned and
lubed moving surfaces, checked for any rotor play or damage- no difference.
Thought that maybe fluid had become contaminated or air introduced into
system during hibernation, bled using M*tyV*c- prop valve, rr, lr, rf, lf,
prop valve again- no difference. Pedal feels ok sitting at idle, out of
gear, but I put it in gear, drive 40 feet down the driveway, apply the
brakes, the pedal goes down very easily about halfway, then feels like it is
intermittently "grabbing" at the right front. I am now believing that one of
the above items is bad, but it would be too expensive at the moment for me
to take the "shotgun" approach, and start replacing everything. Any BTDT
with these symptoms?
	Also, since I will have to get these parts at the FLAPS, (instead of
my normal "go to" source, Rod at TPC)  are there any "extra" items needed,
and any names of parts that might differ from the FA or Bentley names?

   TIA,
	Tyson