Just a point about the three posters piccies above all take the feed off the threaded depth stop, not a good idea but easy route to take. As we all know threads have tolerances and in turn play then more importantly the threaded bar is able to move vertically with its own tolerance on top.
Ideally need off the quill its direct which just means making a bored in cylindrical clamp, with required offset.
Old piccy circa 2006 just done a quick job here and bolted to the quill casting with C type scale on left of head set back. Plus can see where I still have the cheap vertical scale mounting block, there was another above on the head to clear the depth stop much needed.
http://pic20.picturetrail.com/VOL15/728921/1252422/392394060.jpgI haven't got a picky uploaded of the other mill now sold but that like above had the coolant and tap off the quill as well.