I finally got my Constrictor Conloys built up with Harden hubs, but as you can see here, the high cog on this 4-speed freewheel is very close to the stay/dropout. I don't think there is any chance of a plunger-style derailleur ie: Benelux, Simplex, Resilion,

etc. getting to this small sprocket, so I might have to go later than the frameset (late-40's) when I am making a derailleur selection. If I have to, I have to.
I would consider using a spacer to bring the derailleur to the drive side more, if need-be, but there is no room for a spacer on that side of the axle, and the hub axle is not threaded in the center, so not adjustable.
Will early Campy Record/ Gran Sport hit it?