Seems simple... How do you think It will work out?

http://www.instructables.com/image/F...The-design.jpg

or here if the picture won't show by itself.

http://www.instructables.com/id/maki...lling-machine/

Obviously adjust the dimensions to match your application. Is there
something better that might make it easier to square and repeat alignment
upon removal and remounting of the vise? The only think I can think of is
to mount an alignment bar on the bottom of the vise that will drop in the
table t-slots.