Interesting. I don't know; difficult to imagine the function of that weight being replaced by something else, but if your metering block hasn't got one, it probably never did. I'm not sure what I would do in this position.
Still a toss-up, then, maybe leaning toward re-use old.
I'm not concerned just yet, but please show us some pics of what Daytona sent you for an inlet needle/seat assembly.
Interesting. Your slot-one-hole and tweak-the-bracket ideas will be fine.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Instinct will rule this one. So I've done.
Best pic I've got since it's already assembled: Image
It's basically just machined flat like that all around the lower end. As far as the needle (and seat), they are pretty much identical to this one here.
I tested it by lightly blowing through the seat with the needle "closed", and no air came past.
Great!

Aw, fer crumb's sake. Daytona-guy sends Holley-type inlet assemblies in Carter kits, and apparently does the opposite with Holley kits. I donno, give the new one a try; it's a better idea than re-using the old one. But I'm putting another black mark against Daytona in my Book. Two of them, for the apparently-sloppy power valve diaphragm.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Tank is coming tomorrow, Gd willing.
Will probably install over the weekend.
What would the notable difference be between the Holley-type needle/seat vs Carter-type?

Anything cool to know about when removing the tank? Any special procedure for the fuel sending unit?
Side q, will the fuel pump break if I blow air towards/thru it at the carb fuel inlet hose to push the old fuel out the pipes (towards the direction of the [disconnected] tank)?

In the Holley-type assembly, gasoline exits the fitting radially, outward through the sides. In the Carter-type, gasoline exits axially, around and behind the needle.
Don't be too shocked if the hanger bolts break off. New hanger and bolts/nuts are available.
Non-sparking drift (wooden dowel, for example) to loosen the lock ring. Replace the gasket and the fuel strainer and the short piece of fuel hose between the sender and the hardline. Don't leave off the ground clip that bridges this short piece of hose.
If the pump's valves are any good, all you'll do is pressurize the line betwen the carb and the fuel pump. You'll need to disconnect the fuel pump inlet and clear the line rearward from there, then blow into the fuel pump inlet to clear the pump and line to the carb, then replace the rubber hose between the hardline and the pump inlet.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Right, so... First start with the rebuilt carb went as follows:

I cleaned out the fuel pump and all lines going to the carb (plus new filter), rigged a jerry can to the inlet, and started up.
Running all nice and smooth - the least shaky it's ever been - BUT, now there's white(/bluish?) smoke pluming from the exhaust.

I'm confused -- why would anything carb related cause this to happen? Is it too rich? Wouldn't that produce black smoke?

How clean was that jerry can before the gasoline went in it?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Gave it a few rinses with water before filling up... It was relatively new.

Water? Then I hope you dried it quite thoroughly. And the gasoline you used, it was known to be uncontaminated by oil?

Assuming so, it's time for more diagnosis. How much smoke are we talking about, and how thick and persistent is it? Does it increase on acceleration? If the engine speed is held higher than idle for awhile (say, 10 seconds) does it clear up at all, or just keep on at the same thickness? What does the smoke smell like?

Pull the PCV valve out the valve cover and squirt some spray carb cleaner in with the engine running at a fast idle, then (with the PCV valve still not in the valve cover) wait a few moments and check if there's any change in the volume of smoke. Then reinstall the valve and check again.

And please disambiguate "All nice and smooth" (which sounds A-OK) versus "The least shaky it's ever been" which sounds like it's still shaking).

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I had my truck smoke terribly when I started it up after it had set for over a year, when it was wrecked. The gas was old (obviously) but it smoked really bad. I ran it for hours to run the tank down low and then went and filled it up with new gas and it quit smoking completely. Never seen anything like it! Even took a video of it because it was so weird.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

From what I can remember, the smoke was "pulsing" and smelled interesting. Not quite sure how to place it. It was strong, though.
The engine was kept running 'till hot and the smoke persisted. If I remember correctly, the quantity increased with acceleration.
Here's a short video w/ audio: https://i.imgur.com/8WEPmrS.mp4
I did not dry the can before fill up....

I'm away 'till Thursday, will circle back with some more info then. I appreciate all the advice.
I suppose the lower end of the "shake" spectrum I refer to is in the territory of normal engine vibrations.

The pulsing is interesting…makes me think there's either a problem in one cylinder or a problem in five cylinders. Movie is brief, but sounds like the engine is firing on all six cylinders.

Smoke density is too thin/background too light and busy to clearly discern whether it looks more like oil smoke or coolant smoke. Can you use some more adjectives than "interesting" to describe the smell?

Pull the spark plugs. Keep track of which is which (punch six holes in cardboard, label them 1-6, and put the plugs in, tip side up) then show us clear, sharp, well-lit photos of all six tips.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Definitely just a very strong fuel smell. I can't really place anything other than that.
Will have that tomorrow, hopefully.

I ran it again today and collected more info.
It's running smooth now only on cold start/closed choke/fast idle. As the choke opens (and fast idle drops), it gets worse and more shaky.
The idle adjustment screw has very little effect - though if I screw it in too much or too little, it gets more shaky/near stall. But micro adjustments have seemingly no effect.
The smoke doesn't appear at first at all, only once the engine gets hotter (or the idle speed decreases?).

Some better movies:
Starting warm w/ accel: https://i.imgur.com/bdwaQN8.mp4
A few minutes later w/ engine view: https://i.imgur.com/7CNTS9e.mp4
The smoke seems to get more dense as the engine gets hotter.

The valves are definitely very noisey. Have you adjusted the valves? .010 &.020 ? I think it sounds like it has a misfire on one or more cylinders too, but that could be valve adjustment. I'd pull the valve cover and check my valves before doing anything else. It should not sound like that.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Also, what does the engine oil smell like? Pull the dipstick and smell it. Does it smell like gasoline?

Vids at tailpipe look like burning oil and sound like at least one dead (not firing) cylinder. Figure out which cylinder(s) by pulling the spark plug wires off the spark plugs one at a time with the engine idling. Use rubber gloves, and before you do this test remove and replace all six so they're easy to work with. Then start the engine and remove the front plug wire from the plug. Does the idle shake change? Put the plug wire back on. Move on to the next plug wire: does the idle shake change? etc. Take note of which cylinder(s) you can remove the plug wire from without changing the idle quality.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.