The spring hangers have a 4 bolt pattern. The top 2 bolts are closer together than the bottom 2, so the bracket flip is not a direct swap. I've seen some hog out the mounting holes, but to me that seems cheesy and unsafe. Add to this the fact that this alters the pinion angle of the differential. You may end up with a vibration that you didn't have before. I would really suggest that you do not alter the mounting holes.
This is the part where I have to suggest that you have the leaves REarched or to just use a lowering block.
One idea that might be a better way: Check out the spring hangers from AR Engineering. They bolt in like stock but have 2 mounting holes to allow different ride heights.