Dimension changes in J-frames

[Benton]

I just bought a Butler Creek Boot grip for my S&W Model 40. Though the grip is labelled for use on J-frames, it will not fit onto the revolver. The upper rounded cut out in the receiver is a good bit smaller than the portion of the grip to which it should mate. Was there a change in the frame's dimensions since the early 1970s when my gun was built? If so, will a Hogue or Pachmayer fit it properly?

Thanks