http://www.shopsmith.com/ownersite/cata ... rav120.htm
Now as far as added features you can add the incra Telescoping Flip Fence like this one:
http://www.incrementaltools.com/INCRA_T ... c18-31.htm
So again while I'm not sure what features you are looking for there are incra options that might well serve your needs.
If you are looking for a better fit in the miter slot then incra is the way to go. With adjustment there is no play.
If you have other needs well then there are other options above and beyond this that don't require milling a miter bar. Of course if you are bound and determined to mill a miter bar then feel free, just wanted wanted you to know about these other options in care you didn't know.