'96 Outback (Japanese import) Stereo antenna change.

Hello all. I have a 96 Subaru Legacy Outback 2.5. It has the standard double din CD/Tape stereo installed. Removing it is easy but..... the aerial is not a standard push in type or flat type, its basically 2 antenna wires going into the back of the unit, they are held on the rear of the radio by a screw and the 2 inner wires of the coax travel into the unit. Does anyone know how to change this to a standard type so I can install a new radio ?

Many thanks

Grimmy.