I suggest swaging your venturis oversize on the outside diameter, and cutting them to a press-fit. The potmetal continues to shrink with time, and it will again be a slip-fit in a few years! Ideally, you could easily cut one from aluminum to a slip-fit as well. (Beware of commercial offerings that are copies of shrunken originals!)
Note also that you may be able to take a 1 1/4" Model venturi bore out to the neighborhood of 1.150".
That, and shaved shafts with soldered-in discs instead of screws, can increase your top cfm significantly.
For the shim/seal, I cut PEEK:
A thin wafer saves many venturies that have egged holes for the nozzle spigot.
A thicker seal that maybe more convenient for you is the phenolic gasket found in XA and 841 carbs, as well as K's:
JAMES Gaskets now offers them under the -52 part number.
I'm a little confused about the "5/16 BSF allen-head screw".
Were the original threads for the HS needle damaged that badly?
Or is that the same a 1/4"-40 NSF?
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