Two things which will likely improve any Ruger big bore single action are to make sure the throats are correct and firelap out the constriction where the barrel threads into the frame.
Ruger 44. Magnums IME have great throats but the .45 Colts can be iffy. If they are tight a trip to cylindersmith.com will get them a perfect .4525" for cast. There are a couple of firelapping kits available to open up the constriction common to Ruger big bores, I've use the LBT kit in the past or just Wheeler 320 grit recently.
Results can be "better" to spectacular depending on how bad the measurements were off to begin with. I don't know how much cylindersmith charges these days to open throats but it's real reasonable (you only mail in the cylinder) and firelapping is very cheap.
A trigger job never hurts but that can apply to just about any Ruger revolver.
These were shot with a 5 1/2" stainless Bisley .45 Colt after the above remedies. All groups over bags at 25 yards.
Lee 255 RF, 10.0 Unique. 6 shots into 1".
RCBS 270 SAA, again 10.0 Unique. 6 shots in 1 1/8". This is a warmish load recoil-wise but easy enough to shoot in the Bisley.
Back to the Lee 255 RF with 8.0 231 - 9 good shots with an "oops!". Those 9 (this is really two five shots groups on top of each other) went into 1 5/8". Got the load of 8.0 231 from a Dave Scovill article and it has been a great load in every .45 Colt I've used it in.
You can add doodads like a Belt Mountain cylinder pin, I have one and just went back to the factory pin since I couldn't see any difference in accuracy and I didn't need to carry a hex wrench with me to remove the cylinder.
New sights are nice but I've never really needed those either. The real improvement I can see from a new rear sight is more positive windage clicks, Ruger rear sights are horribly mushy in that regard and windage clicks are a real sometime thing.