I bought a replacement mast for mine at one point, then didn't use it since in mine, the cable was broken. The mast is cheap, and not too difficult to replace. The cable is a real pain to replace.
The cable stays with the motor, the mast is a separate piece.
For mine, I replaced my power antenna with a universal one. The trick is to keep the pieces of the factory unit that go on either side of the steel, since these are at the correct angle. You'll need to make up the lower mount, but that's simple enough.