I suspect a venturi leak may be causing it to slurp some extra liquid fuel in every now and then.  I'll consider sending it out in the future for a full rebuild, but in the mean time I wanted to investigate if there are any "upgrade" (e.g. performance, reliability) options.

I know you can buy Chineese knockoff of the MS carb "style" for under $50.

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Uncle Tony's Garage channel on YouTube the other day had an episode on stumbling/missing points style engines. Your problem seems like what he said was an old school problem: chasing fuel, plugs, points, condenser... When the real problem is a worn distributor shaft. Fix was to tighten the points gap to compensate, or replace the distributor shaft and bushings.

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Looks like the following MS carbs were on CAs (with Zenith replacement)

Very possible, it has been in the back of my mind.  But I do know the carb has issues.  It's running a bit too rich.  It starts really good though.  Barely has to turn over at all and fires right up.  My brother said it fires before it even rotates :)

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I bought a harbor freight mini ultra sonic cleaner ($80) and put several carbs through it. Really helps. Dawn dish soap and green/purple cleaner and hot water. Better than a rebuild kit.

Split the carb and put split side down. A little basket from an office desk set for small bits. All fits.

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US cleaner is no match for the chemical  concoction and mechanical scrubbing and passageway cleaning I used.  There's not a spec of rust or other coating.  Replaceable Jets were replaced with new.  The venturi on the other hand is made out of zinc and portions of it look like swiss cheese.  It is likely that it at the very least is not sealing well.  A venturi wasn't provided in any of the kits I could find, but I just found one online and I'll install it in May on my next trip.  A damaged venturi can definitely cause erratic firing due to inconsistent mixture, but it may have more than one cause.  We shall see.  We inspected the distributor when we reassembled and didn't notice any unusual play, but will consider that next.

Venturi's usually don't come in Carb rebuilding kits. To many variables between Carburetors. Some can be purchased seperately. Some of the replacements now are plastic but do the same job as their brass or cast counterparts. If you suspect it's running rich, you should see black smoke coming out of the stack. Check the condition of the floats and make sure they aren't taking on fuel which will make them sink. Easy way to tell, is remove them and give them a gentle shake. If you hear sloshing, time for a set of floats and that is probably your rich issue.....HTH

Steve@B&B

I found a machined venturi online (may be aluminum, it doesn't specify).  The original zink one is in bad shape.  I did check the float, it is fine.  Previously the needle was sticking (new needle, old seat, the flats on the needle were getting stuck in the screw driver slots...finally got the old seat out and new one in, no more sticking).  However it still blows tiny, sparse specks of carbon, not really lots of black smoke though.  Engine newly rebuilt.

Cool, I didn't find it a year ago.  I got one from Steiners.  Anyway I'm not confident a the new one will work, but was cheaper than a new carburetor...if it does.