Grips for Ruger guns interchange very well as long as you make sure that you have matched the grips to the grip frame. Different models of Ruger revolvers can have different grip frames. If the grips match the grip frame...there is normally no fitting required...however, some grips will matchup better than others...but, they will fit and be functional with no problem.
There is one caveat to this...if you happen to have a gun with the lock...it requires grips with a relief cut in the grips.
This is a pretty thorough explanation of all of the Ruger grip frames...will give you an idea of what you will need to fit your gun.
http://www.gunblast.com/Hamm_Ruger-SA-GripFrames.htm