The dots that P-T IWI install on the ramps did not work for me. I sat down with them explained what I call the 'Wiegand method' of front sight installation. The front ramp on my S&W revovlers was integral with the barrel, we milled the ramp off completely and cut a dovetail in the rib. A black front sight of the proper height (just happens to be the front sight from a SIG auto) with the tritium insert is then set in the dovetail. I have seen one of Terry Peters (a poster here) guns done this way also. When Barry Mowery owned IWI he could do the rear dots with a cut that opened up the fixed rear sight on the S&W. Dave Gregor, the current owner of IWI, discontinued that option as he believed that the cut weakened the frame. The dovetail front was a good idea (even got a black sight on a SS gun that way) that Dave set out to do a rear. IWI now has a black dovetail fixed rear sight for the fix sighted S&W revolver. Looks good and works well.
IWI has a pin in replacement front blade for the 640-1, your mod 66 ramp is probably one piece with the barrel and would have to use the Wiegand method. Your 640-1 rear might accept the new fixed rear, but you would need to check because I have only seen them done on K-frames. The 66 has an adjustable rear and IWI has a replacemement blade for the rear sight.
