Does the Single Six have a flat top receiver and a drift adjustable rear sight? If so, don't mess it up by trying to machine for a fully adjustable one. Enjoy it for what it is.
On the other hand, if the rear sight is fully adjustable for windage and elevation, original equipment replacement rear sights are available from Ruger at a modest cost. Aftermarket all-steel rear sights are also available from Bowen Classic Arms for about $90. Millett also made an alumunum after market sight, but personally, I don't like them. The Ruger fully adjustable sights are quite serviceable for all but the most demanding target shooters.
Unfinished steel gripframes are available from Ruger, Brownells and sometimes Midway. Lots of unnecessary cost for a Single Six, IMO.