Well, I 'fixed' it today. I borrowed my friend's Edelbrock 625 or 650 or whatever, slapped it on, fired it up, and it's trouble-free. I know, I know, that's 'parts replacement'. Not helpful. Well, at least now I know it's the carb. I'm going to accumulate some money and look into a Proform metering block (the ported vacuum port on mine is blocked off by a broken tube) and a rebuild kit.

In fact, I have an extra set of fuel bowls with brass floats. I might try them instead of the plastic floats. Anyway, the needles and seats will get replaced as well.

I did notice that the center of the main body that attaches to the metering plate wasn't true, and was bowed inward by about .006 in the center. Maybe that had something to do with everything not working right? I will also stick some carb cleaning pipe cleaner in through every hole.

Just so everyone knows, I'm not giving up on the Holley. I am just glad the issue is resolved.