The drawing here on Sailboatdata https://sailboatdata.com/sailboat/phantom-14-howmar/ should help. The three aluminum spars look like they should be the mast and two lateen booms. The sheet looks like it has a wire or line across the transom that it slides back & forth on. It then goes up to a block on the underside of the lower boom, forward to another block on the boom, and then down to the helmsman’s hand or possibly a swivel cleat; the drawing isn’t clear on that point.
The drawing should also give you a good idea of the rudder and daggerboard shapes, which you could fashion out of plywood. So long as it fits in the slot the exact dimensions won’t be over-critical. You will want to fiberglass or epoxy over the plywood foils to keep water out and prevent them delaminating. Though they might be easier to find, simple boards would tend to warp more easily than plywood.
