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Plenty of junked engines floating around (carby still good, although i'd chuck a diaphragm seal on it
Indeed
It is good practice to replace the diaphragm and all gaskets. including the manifold gasket.
Briggs may still offer an overhaul kit ...?

The other point to note on any s/hand 6 and 8 series is carby butterfly shaft wear.
Any sideplay will interfere with correct carburetion and running of the engine.

This was particularly noticeable with poorly maintained air cleaners.
I recommend new, oiled air cleaners at any overhaul (if engine has a foam filter).

There are serviceable second-hand carbies - but buyer beware.

Hope this helps.
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Jack