Within the 2nd and 3rd generation traditional D/A autos with slide mounted safetys, hammers and triggers interchange regardless of frame size or caliber. However, there are two lengths of hammer struts but if you buy a hammer with the wrong length strut you can reuse your original strut. Second generation hammers have a half cock notch that was eliminated in 3rd gen. hammers because its safety function was redundant to the slide's firing pin blocking safety plunger and the sear dragging across the half cock notch could be felt during the DA pull. The silver colored hammers and triggers were flash crome plated non-stainless parts. There are two sizes of safety assemblies: 9mm/.40 and .45/10mm. 745s used huge single sided safety paddles. All other 2nd & 3rd gen. single sided safetys may be after market parts, but I'm not sure.

Gil