Still working off some broad assumptions, some AI, some Google, and guessing; i find what May be a replacement shaft, atleast for a similar tiller, for $315. Now, please dont take any of that as gospel.
At that point, assuming you ID that this Is the right part, I would assess the over all condition, and decide. Maybe its worth it, but make sure the rest still has years of service left in it. I still dont like the wear on the top, out-put axle shaft; and if we start talking about $600-700 worth of shafts, possibly sprockets, chains, and still a 30-40 year old impliment, I start atleast questioning if its the right choice to rebuild it.
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