I have a few NOS or nearly NOS Regina 5 speed freewheels (some ORO) that would of course be appropriate. I can also set you up with Shimano 600 6 speed that are pretty nice. I'd personally run a new SRAM or KMC 8 speed chain on a 5 or 6 speed freewheel. They cross chain nicely to the big-big or little-little combo.