Carb issue?

Elevation 6000 ft?
IMHO, you got the wrong cam for that elevation.
But lets see if we can get something out of it.

Ok so a lil explanation might be in order;
At idle
Your engine is pulling fuel from the Idle Discharge ports and the transfer slots, and should not be getting fuel from any place else. You control how much fuel by the synchronizing of the mixture discharge with the transfer discharge to ballpark it lean enough to idle but not so lean as to have a tip-in issue.
However, at this setting, the long-period cammed engine is usually begging for more air or more timing. Too much timing will just drive the rpm up, so that is not the answer. So you pick a timing that is known to be in the ballpark, by what others have empirically amassed like 14 to 20 degrees. And after that, you have to decrease the excess fuel, or supply the additional air, to get the AFR back into a decent working range. And that's all there is to it,basically.
So to help you figure it out;
Try this;
Remove the springs from underneath the metering rod pistons.
Defeat the Vacuum advance.
Close the mixture screws to 2.5 turns.
Close the secondaries up tight but not sticking.
Prove the fuel level is correct and stable.
Make sure the PCV SYSTEM is plumbed correctly and working.
Make sure the distributor flyweights are at minimum setting and stay there to at least 1200rpm for this test.
now
Fire it up and
crank the idle speed up to where the engine idles nice, say 1000 rpm, or whatever it takes.
Without regard for the timing numbers, just advance the timing until the rpm peaks.
drop the rpm back to 1000
readjust the timing for max rpm. Write the timing and rpm numbers down. I might want to refer to these later. I just want you to see how much Idle-timing your engine is asking for
Next;
start taking timing out of it, while simultaneously readjusting the idle speed screw to maintain a minimum 800/850rpm.... until you get down to 18/16 degrees advance. Forget about the vacuum reading. Forget about how she runs, just see if she will do it.
Once you got her running there, you will need to figure out if she is rich or lean. You already proved that she is rich by cracking the secondaries and noting the increase in rpm.
So, the question is how to; give the engine the air she is craving, or subtracting the too much fuel that she is getting. Which method you chose will depend on where the throttle blades are at idle, relative to the transfer slots.
Ok then
Remove the carb, drain it, put the primary throttle on the curb-idle screw and keep it there; then flip it upside down and go find the transfer slots. They will be on the very front of the bores, and are the only vertically oriented slots there. You should be seeing them as slots a little taller than wide. NOT more than about 30% taller than wide, and not less than 20% taller than wide. I'm sorta guessing but that will ballpark them. Make them so. Then bolt her back on, and fill her up.
After this, DO NOT adjust the speed screw again! If the rpm is not right (which is a personal preference, somewhere between say 700 and 850), you will need to adjust it with timing.
Ok now you are baselined.
To subtract idle fuel you only have three options;
1) mixture screws, and
2) IABs aka Idle-Air-Bleeds, and
3) fuel level
To add idle air, IMO you only have two options;
4) drill holes in the primary throttles, as mentioned, or
5) cracking the secondaries.

Of these, I am no fan of introducing dry air into the secondaries, and no fan of messing with the factory fuel level.

I also don't like to get too far away from 2.5 turns of the mixture screws.
So really, you only have two options; numbers 2 and 4.
Unless your carb was designed to run at 6000 ft, it has the wrong IABs in it, and so that is where I would start. But I can almost guarantee you that, your engine will still need bypass air thru the blades sooner or later.

So at this point, I am out of my comfort zone with your combo, and someone else with hi-altitude experience can take over.

But I want to reiterate, to leave your transfer slot exposure, underneath the primary blades, very close to the above ballpark of a little taller than wide. Don't care what the idle timing is to get it. If you get too far away from there, you will have driveability issues.

Now after your idle is bugged out, there is a small matter of the missing springs under the step-up pistons to figure out, and at some point in the near future, the Power-Timing will have to be addressed, and later, the missing Vcan.
That's all I got.
Hopefully someone smarter than me will stop in.