I had the same issue with my rented garage, so i ripped off the doors n frame and just about got it in and put some swing away doors as a replacement.
For your issue though, you say part of the building is above the drive, have you looked into how this is built? Some buildings have an awful lot of wasted material on top ( or below ) depending on the age of the building, you may have 4" of space above the drive which has been boarded up for no reason other than asthetic.
Other than that, drop down into the drive abit to get some clearance but make sure the distance you begin the drop is 3/4 the length of you landy away from the underside of the building.
Any chance of some pics?