Since it is a fitted part and since people could get hurt, literally, it is something you should let a professional install.
I am not kidding when I say that one file stroke too many on the lug of the thumb safety that fits tightly up against the sear and it will allow an unsafe condition and there is no going back.
One file stroke too many and the safety is ruined. If you insist on trying this yourself, buy three and plan to ruin the first two. Or, just have it installed by a professional.
In addition to the three thumb safeties, you will need the jig, the proper file, a bench vise, etc. And, you will need to carefully study a few dozen You Tube videos. Most have such poor camera work you cannot really see what the installer is doing. I think the videos by Wilson Combat and Heirloom Precision have the best camera work as does the one that shows the lady at Colt assembling the Colt Government Model and fitting the thumb safety.
The S&W 1911 does use standard 1911 parts. Any company making a reputable thumb safety for the 1911 will make it oversize and it will require very careful fitting. Very careful.
Here is a video showing how Colt fits a safety during assembly of a new 1911. Next there are videos from two highly regarded 1911 gunsmiths - Jason Burton of Heirloom Precision and Master Pistolsmith Ron Phillips of Wilson Combat.
Assembling a Colt 1911 at the Colt factory | Ever wonder how a Government Model 1911 is assembled at the Colt factory? Here is an excerpt from Panteao**™s Colt Model of 1911 documentary video. For... | By Panteao ProductionsFacebook
https://www.youtube.com/watch?v=9zF3xCZ6CrE
https://www.youtube.com/watch?v=Rd5m-Adc97o