Is it confirmed its a rod-bearing...?

Maybe the petrol has stuffed up an injector...

A bad injector can make a terrible knock on one cylinder....

The use of petrol by mistake does not necessarily wreck an old 617--Even if driven for a few days. Usual issues are vapour locking and the car stopping when its fully warmed up.

Apart from possible damage to the injection-pump, (You'll know about that PDQ) the engine itself wont care much about some petrol in the fuel, although the additives in the petrol could dislodge crud and make an injector spray-pattern crappy, leading to a combustion-knock very akin to a failed rod bearing.

--This is through Experience--And Not Anecdotal Evidence like many spout about mis-fuelling cars....

Thing with mis-fuelling, Garages rub their hands with glee at the sound of it, saying Everything needs replacing, pumps, injectors fuel-lines--you name it, even if the car is still running hence promoting the notion of death by wrong fuel!
--When all they (Usually do to repair) is to replace the fuel and the fuel-filters!

If it were me buying it, and I could confirm its Not a bearing I would happily buy it, I wouldn't give the petrol thing a second thought.

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http://i190.photobucket.com/albums/z...0TDnoplate.jpg

Alastair AKA H.C.II South Wales, U.K. based member

W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....