The G&P kit requires a three piece barrel, so a little work is require.
IIRC, the issue is that the grip is longer/shorter than a regular one, so you have to move it along with the sight either by retaping of epoxying the assembly.
The light it self is nice, but you might want to consider another route to add a taclight to your setup:
http://www.lapolicegear.com/caatrramofor.html