Typically the height from the bottom of the keel to the top of the flying bridge (venturi wind screen) is 13'x 9". This does not include the mast (it will have to be laid down). Your transportation company will (should) have a specially-designed trailer which will minimize the distance between the keel and the road surface. GB32s are transported this way routinely.
Good luck! And remember, this is the Internet! I might be making this all up, so check with the current owner of the boat or measure yourself...