You might consider ordering the “The Historic Wood Canoe and Boat Company Catalog Collection” on CD, from the WCHA online bookstore --
http://store.wcha.org/The-Historic-...pany-Catalog-Collection-Version-2-CD-ROM.html
It contains copies of many of the Morris catalogues (as well as catalogues of many other companies), which give dimensions, location of thwarts, and details of the various Morris models (such as gunwale profiles), and show pictures of things like the various decks.
I don’t know that plans or patterns for seats are available. Here are some pictures (click on thumbnails to enlarge) of the seats from my 18’ Morris as bought, with plastic cane, with some measurements. (I have removed the plastic cane, repaired cracks between holes, refinished and recaned). The ends of the lateral rails are angled to match the line of the gunwales. The fore-aft measurement of both the bow and stern seats is the same. As you can see, the outside edges of the top of the seat frame are rounded except at the ends and in the corners; on the bottom of the frame, the edges are all somewhat eased, but not rounded in the same way. As memory serves, the frame rails are 3/4 inch thick x 1 3/4 inch wide.
stern seat
bow seat
repaired, refinished, recaned.
I believe the basic dimensions of the caned area would be the same for a 16’ Morris, with perhaps some minor difference in the overall width. The beam of the canoe may well be a bit different from when it was built – shapes and dimensions often change over the decades, depending on how the canoe was stored and used.
Morris seats and thwarts and decks were mahogany. Long-decked Morrises had mahogany outwales and spruce inwales stained to match; small-decked Morrises had spruce gunwales. Other wood parts are cedar, including the stems (which is usually a hard wood in other makers’ canoes).