I pulled a 401 set and a 301 set and compared.
The ruffler is the same (same part number) the other feet are the same except that those for the 401 have a wider needle hole to accommodate moving the needle right or left. The dimensions other than that are the same.
So I'd conclude you will have no problem using feet for the 401 on a 301 - an using those for a 301 on a 401 Provided that you keep the needle in the center position.