Yes, this was removed by previous owner to free up potential horsepower, if you are looking in replacing it here is just one place for referral to assist you:
http://www.latemodelrestoration.com/products/Mustang-AC-Conversion-Kits
mind you this is just a referral not necessarily the best deal out there, though it may be. Oh just incase the horsepower from that delete was anywhere from 5 to 15hp depending on motor, nothing compared to riding with the ac blowing. Good Luck :bigthumbsup