Feel free to ignore as this isn't really answering your question, but why are you replacing it? It looks in decent shape in the picture. It also looks very similar to the bulkhead/chainplate setup on my old C36, so I'm suspecting you are replacing due to some
rot just below where the chainplate passes through the
deck. If this is the case, and the area of
rot isn't huge, it's unlikely you need to replace the entire bulkhead.
Mark and cut out a rectangle a little larger than the rotted area and pop in some new
marine plywood cut to the same dims. You could
epoxy it in place or add a bridge plate on the backside that looks to be inside a
storage compartment. Cosmetically, you could play around with stains or oils on some scrap ply to roughly color match the existing bulkhead.