If he has "full papers" as in full ANKC registration papers as you say then please contact his breeder, if they are a truly ethical breeder who care about their dogs then they will take him back or at the very least help you in finding a suitable new home for him. He cannot just go to anyone, being that he is dog aggressive he needs a suitable home who are experienced and prepared to manage him with those issues for the rest of his life, not an easy thing to do (I know I deal with it everyday).
Like Jadie suggested I would be putting up an adoption price for him, even though he is desexed he is a very possible target for dog fighters to take as a bait dog. These people can present fantastic fronts that look like really legitimate people to take him on.
I would avoid Best Friends personally, I have had dealings with them, and although Bull breed "friendly" have heard some of their volunteers saying things such as "Staffy's have lockjaw" a myth that has been debunked for many years.
In all honesty most foster carers have their own animals so he is probably better off staying with you until something else is found. Many rescue organisations will allow you to "advertise" your dog through them as a "private rescue".
Here are a few you can try to contact.
Animal Rescue Qld - Home
Red Collar Rescue | Biggenden | Welcome
Also there is a facebook page called "Bull Breeds in Need", if you message them they may place him up on the site for you as well.
If you post up a picture of Chase I can speak to a few people I know in Queensland who have breed experience and may know people who are experienced owners, who are looking for a dog.
Another rescue org to contact
Puppy Love Rescue
Puppy Love's member profile at PetRescue
They are only a small, NSW based rescue, but they deal mainly with Bull breeds and have lots of experience with them. They have a facebook page as well but I can't access FB from work so I can't link it. Just search Puppy Love Rescue though. I am sure if you contact them they may be able to help or at least give you some pointers.