Originally Posted by
well biked
Sheldon says the only difference is the thread pitch, and it will work. But once you do that, it seems you shouldn't go back and forth between English and Italian threaded freewheels. Look in Sheldon's glossary under "Italian," he discusses it there.
The difference isn't exactly the thread pitch (i.e. the number of threads per inch) which is the same, but the thread form. English threads have a 60° included angle while the Italian threads are 55°. As noted they will work with each other but once you make the change, stick with the new thread form.