Your Lyman manual has data for 250 grain rnfp bullets, Lyman #452664.
All the manuals you listed have "Ruger Only" data for their bullets; Lyman has some too, and while it's not exactly the same bullet, you can review that data and get an idea of where to start with your load workup.
I load a Beartooth 255 grain RNFP with 13 grains Blue Dot (taken from Speer #13 with their 260 grain jhp data) and get about 1000 fps from my 3-3/4" Montado.
I don't keep max pressure "Ruger Only" loads around anymore as I don't have a large frame Ruger in 45 Colt now. I sold them off along with my 454's and went to the 480 Ruger for big chores. But when I did, I only loaded "RO" loads in Starline brass. ALL of my low pressure loads for my Montado was with nickel plated Starline or WW brass cases.
The point I'm making is you need to have a fool proof standard rule that you never break to make darn sure your RO loads don't accidently get loaded into your S&W Governor.