Quick update: It looks like the combination of new rear brake hardware and a Master Cylinder rebuilt kit from NAPA has fixed our issue. I'm not sure which one did the trick, but by the look of the brown MUD we found in the guts of the Master Cylinder, I'd say that was probably it. Since we were there, I replaced bushings on the clutch/brake pedals and readjusted pedal clearances. As always, there's never a good place to stop on these old rigs. But I got to spend a few more mornings with my Pop, so it was worth it for sure.
