A Shimano freewheel will be nice for that Bianchi and will last many seasons. The Park Tool FR-6 or similar is required for service.
https://www.jensonusa.com/Park-Tool-FR-6
https://www.jensonusa.com/Shimano-DX...peed-Freewheel
40 bucks and done. Probably less if you shop around.
-Tim-