When we purchased our 45C, the bottom "rub rail" part had been ripped out of the starboard side. This was part of some hurricane damage the boat sustained and that part, including its stainless steel rail, were both lost.
We had a new rail made from a solid block of mahogany, formed following dimensions from the port side rub rail, which was still intact. This was a lengthy process, as the part has many curves and must meet the hull curvature as well. The stainless steel rail, we were able to cut out from a longer rail, recycled from boats that were destroyed during the Hurricane. We cut to our required length and bent it as needed.
Before installation, the wooden piece was sealed up I'm not sure with what.
The previous part had been held on with carriage bolts, from the inside of the hull, as mentioned before. Accessing these bolts would have been impossible for us so we used stainless steel self tapping screws, countersunk into the part. Used a liberal amount of 5200 on the screws and between the part and the hull. Paint was "easy", since we were already painting the whole boat.
Good luck,
JCG