The problem with this is that as the axle moves forward, so does the tie rod, and if its far enough forward, then the tie rod will interfer with the drag link. Basically, the ideal location to mount the box is as far forward as possible. The crucial point then becomes the pitman arm to the spring pack. If you can get this clearance down to about 1/2" then your looking really good. Also, with more of an angle on the tierod to the passenger side steering arm you have, the less bump steer will occur (which is already nil anyways).
Regards,
BigMike