Hello Rick53. Of the PGW's parts, only the firing pin extension is what would most likely be a "drop in". The short stroke kit and carrier most definitely requires fitting to your gun. It's not hard, but you do need to understand the timing of a '73 to get it right. There are no aftermarket light springs that I am aware of so that means modifying the factory springs. Again, not hard, but some previous experience is desireable. If you go too far, replacement parts can be a problem. I install the lever safety spring that PGW's sells for the Uberti, but that requires modificatiion of both the Uberti spring and the Miroku spring.
Unless you plan on using the gun in very serious SASS competition you really do not need a short stroke kit. Also, SS kits are not legal for NCOWS.
If you are not comfortable doing your own work, I would recommend PGW, Longhunter, Lassiter or Cody Conagher. You can Goggle these folks for more info. Cody's approach to short stroking is different in that he modifies the factory parts instead of installing all new ones. You might ask around your area to see if there are some good cowboy gunsmiths available locally.
The Miroku '73's are quite useable right out of the box, but there is no comparison to a really slicked up version if you want to use it for CAS competition.
TR