Ben Kamenjas asks "...Know where to get these 3 speed freehweels? I'd prefer very good or even new ..."
One option is to assemble a 3-speed freewheel from disassembled Regina Corse/Corsa/Etc freewheels using their cogs and the Regina scalare (close ratio) freewheel body. Compare the cutaway profiles of the 3-speed freewheel (not the Sport version) and the scalare 5-speed freewheel in the Regina catalogue on Robert Broderick's catalogue site. The cutaways show a slight difference in cog spacing between the threads for the largest cog and the next largest cog, but in practice, that spacing may not be significant. I checked this out with a loose scalare body and loose cogs, and it looks promising.
La Jolla California USA