Well it took forever but I got the LF brake caliper rebuilt, reinstalled it today. It's functionally the same as a BMW 2002 tii or 3.0 coupe or sedan, but the inlet ports are different.
So installed it all, started to bleed, and go no fluid at the back. Hmm. Pondered and poked, got good fluid at the front, as well as the clutch, which uses the same reservoir. MC is a single circuit Giulia TI part.
After breaking various lines loose at the rear, finally figured I was getting fluid into the proportioning valve but not out of it. It has a moving piston, like a Fiat 124, based on axle height and presumed forward pitch as a result. A little arm connects the piston and rocker shaft, which are mounted on the body, to a link on the trailing link. It's one solid rusted piece, I fear. It's not the same as a 115 proportioning valve, so I'm going to have to figure something out here, route around, hollow it out, make new lines, we'll see. It's not the end of the world, but I was looking forward to gettin' this sucker out of the garage after six weeks. No brakes; not yet.