The engine seems ok under partial throttle. I can run 3500 rpm with 12 inHg vacuum. To run at all, I need to advance the timing as far as the distributor will allow. Idle vacuum readings go from 8 inHg at the 2500rpm condition all the way to almost 0 inHg. It creeps up from ~0 to 2 inHg right before it races back up to 2500 rpm. This has all been done with a "cold" engine in 90-ish degree weather. It sounds like it is surviving on one cylinder at low rpm, but at 3500 and 2500 rpm conditions, I think I hear all 6 cylinders operating.
I got the carb and manifold together over ebay. They were allegedly bolted up to a 280 that somebody was parting out. Best guess is a 390 cfm. It has a dichromate finish, vacuum secondaries, electric choke, and square bowls, so according to holley's website it should be a 390. It has some carbon deposits, but I sprayed carb cleaner all over including into the idle mixture screw holes. It squirted back out the top just under the choke. I don't know what size jets or power valve it has.
The car has been sitting for about 2 years, but it has new oil and freshly flushed fuel lines. (flushed means I hotwired the fuel pump and drained all the crap out into a bucket. I saw no rust or particulates, but I did get a good high. I don't know the full history of the engine, but I have no reason to assume that is has anything fancy. It is still using the stock electronic ignition module. Thanks for your help, folks. I am learning as I go, and I have know enough now to realize how ignorant I am.