I've done this many times and the problem is always getting the bezel crimped back on. Without a lathe and some special tools to press the bezel back down as the speedo body is slowly turned, the only method I've ever got to work is to methodically work round the bezel, pressing the edge down with a wide blunt flat screwdriver. It pays to do two initial 'crimps' on opposite sides to centralize the bezel and then work slowly round. The bad news is that there will always be tell tale marks to show that this has been done. It's only obvious if you look closely, but if you can't live with this then the only other option is to use a professional instrument restorer, but that won't be cheap!
HTH.