Bob, here's a photo (2nd attempt, I am a horrible photographer) of a 4-speed freewheel I grabbed from the parts boxes; I used it in my 1st attempt to use a 543, back in the 1970's. Maybe just enough miles to remove some cog paint It was NIB when I got it. I see the outer removable race is flush with the outer cog, but the removal-tool boss projects a good 1/8" beyond that. Maybe it would fit James' bike... no idea of threading, but it's a 14-to-20T, best suited for rides that are all various grades of downhill. Unsure if anyone could rework it to "sane" tooth count. Anyway, here it is.