Hey guys and girls, referencing the subject...
Car is a 73 Barracuda with stock 10x2.5 drums on the rear.

Symptoms:
Spongy pedal (requires pumping, can't lock F or R brakes)
Clunk from LR on application and release of brakes
Slight fluid leak from both rear cylinders (driver's side cylinder replaced)

I replaced the LR wheel cylinder as pretty much the 1st step in troubleshooting when I discovered that the rear shoe had not returned properly and was outside of the e-brake expander. I un F'ed that, replaced the wheel cylinder, reassembled and adjusted per the manual. All appears in working order on both sides. E-brake works, though the cable is massively stretched.

Will the collective Moparts brain trust get me on track here? Thoughts on where to start?

While I haven't measured the drums, they do not appear out of round and the braking surfaces are in good shape. Pads appear in good order as well. MC pushrod clearance set to .020" using a depth gauge.

Relating to the combination valve, can those things leak internally?

Chris