I just installed my ac air box in the car. No dash installed yet. If you were able to get the clips (or screws) off af the bottom half, there is no clearance to get to the top or sides. And if you tried to pry it open with only the bottom clips removed, IMO it would crack the upper flange(s). Here is where you need the caulking strip installed - see photo.can the box be split without removing it ??