Ward,
Here is a link to a thread about swapping out a bisley grip frame. everything should apply to what you're wanting to do.
http://www.rugerforum.com/phpBB/viewtopic.php?t=27725
You may already know this, but I'm going to throw it out there. Ruger does not "fit" aluminum grip frames to individual guns. I'm not saying that you can't fit them, just that Ruger doesn't bother w/ it. Swapping an aluminum grip frame would be rather easy. Just replace the birds head with the aluminum one, check for function, and you can leave it at that.......Or you can continue to "fit" the frame.
Ruger DOES fit steel grip frames to individual guns.
Why do I bring this up? because it's possible that if you buy a
used steel grip frame, the "ears" may be too low (from previous fitting at the factory) and fitting it to your cylinder frame might be troublesome.
just a few things to consider.
~c.r.