I am unsure as well. At the armorers course they told us that only a few Gen 4 parts can go in pre Gen 4 models, the trigger bar was not one of those parts listed. However, a lot of people are doing this. I have a hard time believing that Glock took a step backwards in design between the Gen 4 and Gen 3 trigger bars. As with all Glock triggers the more you shoot it the better it gets. The bump does cause a different feel in the trigger which reduces the smoothness of it. I would try oiling the bump and section of the slide that it rubs on and see if that helps improve it. I am unsure if these are duty guns or not, as with any CC gun I would refrain from any modification but if this is for target or competition then why not try it out and report back to us on your findings. As for the slide wear comment it may take the coating off but I don't think it would do anything that would affect the reliability of the gun. Hope this helps a little.
Though I walk through the valley of the shadow of death I fear no evil, for I am the meanest mother F***** in the valley!....oorah