To recap: Putting 122S back on the road after a three-year restoration. Loud chirp appears to be coming from the Delco alternator, even with new belt, perfectly aligned and clean pulleys, relube of alternator from the inside, and much fussing around...

Mystery explained, I think -- just back from having a front end alignment done by a real mechanic (as opposed to a technician, or worse yet, artisan...). Guy test drove the car before doing anything, and commented that the chirp only occured under closed throttle. "That's a vacuum chirp, not a belt chirp." Heaved up on the forward Weber and the chirp quit temporarily.

Two sets of Weber soft mounts, the second installed using Hylomar as a sealant, and the mounts adjusted to be perfectly even measuring with calipers, and it still leaks. I can't detect it with starter fluid and it doesn't seem to affect the tuning, but that's undoubtedly the chirp. &%$#!

At least I can get on with fixing what's actually broke now. (And the alignment feels great.)

8^)