Using a 3rd gen box is a great upgrade. Note that there are different boxes in the sense of turning radius. Typically the boxes that came on 3rd gens with 16" wheels had stops installed in the box to limit travel.

This was to prevent the tires from rubbing on the frame. The boxes have a two letter code such as HX or JY to ID them. The HX box was used on 3rd gens with 16" wheels. While the JY box with 15" wheels.



I'd definitely do some searches here and on the 'net for additional information on which would be the best box for your set up.

Bob