401 and 403 are both slant shank machines. They will both zigzag, but the 301 won't. The feet and buttonholers from the 400 machines will work. Items like a zigzag foot will work, but not too well. The 400 machines have a wider space between the feed dogs than the 301, so a zigzag foot will fit on the machine. However, the feed dogs will not line up with the foot. It will kind of work, but not well. Other than that, I think most everything will work. Also, the 403 accessory box may have cams. They won't work on the 301, either.
I happen to have 2 401's, so you hit on something I know about.
By the way, I'm in Texas. It's not on the way to Vancouver. Thanks for the offer, though.
bkay