Here's what happened:
The car was stored from 1979 through about 1997, when I bought it from the original owner, replaced a few critical parts, changed the oil etc, fired it up and drove it. It always had "hard" brakes, not much throw and no sponginess at all. Stopped okay, though. When I slammed on my brakes the other day, the rear wheel cylinders apparently actuated for the first time in 23 years, then stuck (due to rust and crud) in the "out" position, causing the rear wheels to lock up.
Took the cylinders apart, re-honed, cleaned up the pistons, replaced the rubber, put everything back together, bled them and away I went.
My brake pedal is now a lot softer, but I think now all four wheels are braking.
Live and learn. Thanks to all.
Toby