I find cleaning BP residue from under extractor and on spring after several matches can help steer away from possible hick-ups later. I have Snake Oil George's one-piece firing pin and extractor system in mine,. but need is still a good one in any 73 at some point, especially if shooting black. The modification to allow hammer to travel back far enough to slide firing pin assembly out is a handy mod.
I like Sgt Eli's cut on bolt also. SOG does similar cut.
So much to be said for Cody's Codymatics. I shot my share of them thru the years and sold them when in firearms business. Many argue that method is a bit obsolete but there is still much good to say about the smoothness of the CAW. I eventually changed to get on the "new thing" bandwagon. Now shooting C&I 5th gens. Stroke is shorter but not sure I would say the 5th gen any smoother than some of my early Codymatics. I still often wonder if I am any faster with the shorter stroke where I find more resistance in throw versus the smoothness I had in Codymatics.
Incidentally, the Codymatic I would have Cody built me, and thus call the Billy Boots Model, started as 24 inch pistol grip then shortened to 19" (before the 20" barrels were readily available), muzzle was smooth rounded to inside, then most other little mods Cody had in his "bag of tricks". There was a theory at the time that the rounded muzzle dispersed BP smoke better and more like smoke-ring. Not sure that theory was to valid but mod makes good conversation for sure.