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Spent the weekend pulling this off and re-installing several times. I think I have the float where I want it. No leakage into the throat or onto the throttle plates.

I still get a very small seepage from the two jet plugs. This has been a problem since the rebuild. I finally replaced the gaskets from the kit with the old ones (which appeared to be the same, and were undamaged) and it really improved the situation.

I get no leakage at all while running. Even for a couple hours after shutting down, no problems. But, by morning, there is a small amount of gas on the manifold and the plugs are wet to the touch. Very frustrating. I did not "kill" these screws, but they are tight. I am thinking of using two gaskets per screw (I think I used to do this a long, long time ago...) by logically, I can't see how that should help, and it seems like it should make it worse.

Is there anything I can do, use or add that will seal these screws up? I am thinking a little teflon tape, but I don't think that will work for gas.

I won't comment on whether teflon tape is a good idea or not, but it's entirely inert to gasoline (and most everything else as well), so it's certainly a candidate to consider.

Not a carb person and probably reasons why not to do but one of the uses listed for non hardening Permatex is just what you are encountering-seepage around poorly fitting gaskets. Says it is gas resistant but does not say gas proof so that leaves a bit of wiggle room.

If one were really desperate and you had an old carburetor carcass to practice on, you might want to try a technique from the gunsmithing trade used to "bed" steel actions to wood stocks for a perfect, intimate fit. It depends on using "JB Weld" 2-part epoxy which I believe is gasoline resistant.

The method depends critically on the use of a "mold release" agent which is usually an aqueous polyvinyl alcohol solution. Apply the mold release agent to the brass passage plug screw and then apply a THIN film of JB Weld to the damaged threads and plug screw seat, and screw them together. After the JB weld has cured, if you applied the mold release agent carefully the two should be come apart again and the threads will be "repaired" and the fit will be restored and should hold gasoline.

I have used JB Weld before, but never in the manner suggested. I don't think I am that desperate yet (and don't have a spare carb body around), but an interesting technique.
I don't think there is any damage to the threads on either the carb body or the jet plugs. Both appear to be pretty crisp. (But, maybe the seepage means the diameter of the hole has increased over time). It almost seems to me that a gasket from some other material (or a fatter one) would solve the issue. I don't see any deformation of the bowl where is contacts the gasket/screw, no obvious scratches or gouges. But something is certainly up. I think the area gets too hot to use a rubber O-ring.
I would be a little afraid the permatex would get into the float bowl and then potentially clog something, but I may give the screws a single turn of teflon tape. I think this might work as long as the screws still screw in completely.
I do recall when I first bought the car (which had been in a private museum and seen little use for about a decade) that I would note some accumulation of gas on the manifold, which went away after a short while. I hadn't seen the issue for months. I am now wondering if they rebuilt the carb prior to auction and experienced the same problem. Also wondering if it will improve over time.

I wouldn't be apprehensive about using 2 or 3 turns of telfon tape as long as you took care that none could spin off and get into the internals.

Try using the OLD plugs insteat of the new plugs. Maybe lead gaskets instead of the fibre gaskets if that is what they are. REal thin radio solder (no rosin) mite work as a seal if u can hammer it flat and in a circle. But that;s the hard way. I'd try the original plugs first.

One can tin the threads a little bit with some tinners solder but that gets tricky too especialy threading into aluminium.

If the Teflon tape will work then that's the easiest. I've used it often on gasoline lines and so-forth. I've never liked it. There's just been times when i had to use it.

OK, the Teflon tape will be the first shot, probably not till the weekend. I'll let you guys know how it comes out.
No new plugs in the kit, just new gaskets that didn't seem to do the trick. The old gaskets made a world of difference, but still a small leak. Very frustrating...

Thanks for the help!

White metal isn't archival like bronze, brass and copper. There are many variations in alloy and some last better than others, but they are all subject to attack to one degree or another by moisture which of course, when it accumulates in the fuel, lays in the bottom of the float chamber and whatever lower recesses it can get to, and that's where the gradual deterioration starts.

If you wanted to "tin" just a tiny portion of the thread or area where the plug goes and are reluctant to try the JB Weld and mold release method, you might try "Rose Metal", a compatible alloy that melts about at the boiling point of water. Readily available from gunsmithing supply houses. But due to the low boiling point you only want it to fill pits or put the thinnest of layers on damaged threads where the larger mass of the carburetor will act as a heat sink and keep it from remelting.

Assuming teflon tape doesn't work, that and the mold release agent and JB Weld are my best suggestions.