I'm not an gunsmith nor do I play one on TV, but there are two spring loaded buttons that go through the top of the second and third generation slides to operate the various levers below.The first gen slides have only one... that in and of itself would make the swap not work. I don't know whether it would be practical or even possible to alter a first gen slide to do the work of a later one, but there are enough 2nd and 3rd gen slides out there, that it probably wouldn't be economical, IMHO.

Froggie