Billy, I like your thoughts here....... love the .45 Colt cylinder idea on the mdl 83. I'd personally go with a 4-3/4" or 6" barrel though.
I'm not sure where the comments about the 45 Colt cylinder only handling the Ruger Only loads come from.
you can run a 5 shot 45 Colt up to 50K psi while the Ruger Only loads are ~30k psi loads. and by using the shorter 45 colt brass, you're only increasing your choices of bullets that will fit in the FA cylinder.
in a 5-shot 45Colt on the 83 frame, you'll be able to push a 325 grain bullets to ~1500 fps out of a 6" barrel. JMHO, but this is where the 45Colt will outshine the 44 mag.
the warmest ruger only loads will only push that same bullet to ~1275 fps.