After the fiberglass over the tank is cut and the fiberglass securing the tank to the hull is removed the new tank can go in. It looks like a new custom tank will have to be made out of metal or an existing tank made of plastic will have to be modified to fit in the space. A new tank from Catalina will cost over $500 plus shipping and handling. I'd rather pay a local to make the tank than get one shipped up from California for that price. I'm still on deployment so thanks to Josh for starting the project.
Here are more pictures:
View down at the aft starboard bert with covers removed
View from midships aft of the motor and tank

Crud inside the tank. I guess it was time for replacement anyway.