Give Selected Object Same BBox or BBox Changer
Selected Objects Same BBox - set the bounding box size of selected objects to the biggest size on each individual dimension of the selected objects existing bboxes., If possible without having stray vertices in the resulting objects.
Example : Object01 BBox (x=2m y=4m z=1m) : Object02 BBox (x=3m y=1m z=3m) = Resulting BBoxes (x=3m y=4m z=3m)
BBox Changer - allows you to change bounding box sizes of selected objects simply by typing a integer in the X, Y, Z Dimensions within the rollout dialog, then click "Change" button. If possible without having stray vertices in the resulting objects.