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...close ratio freewheels are still around, just not in large numbers. I find them every now and then in the bin at the bike co-op here.

I have started just making up my own, using scrap freewheels I get out of that same bike co-op bin. If you stick with either early Suntour or early Shimano when you collect your parts donors, you get a lot of cogs that are compatible with whatever bodies you end up with that still work, I do not disassemble the bodies, because that requires a delicate touch and good eyesight.

Not sure I understand why, if you got your old freewheel off, you are not simply re-using it after cleaning, flushing, and re-lubricating it ? Is it worn out on one or more cogs ? I've had pretty good luck with replacing cogs on Shimano freewheels, but at this point I have a large collection of them.