Just a little warning. When this or any joined wooden construction is assembled, leave the joints a little tight in the Summer as it is likely to have expanded in the moist atmosphere. In the Winter, make sure the assembly is quite loose as the winter dryness makes the wood smaller. The length of a piece of wood does not change dramatically, but the width and thickness can change significantly. Keep tabs on the humidity trends before doing fine construction in wood. Also, very wide boards can split out nails and pegs as the expand or contract. It is wise to minimize nails and pegs in very wide boards.
Anyone who has worked with a small space will realize what a blessing it would be to reduce the thickness of a wall from 4 1/2 inches to 3/4 of an inch. Cut door openings out of it, and simply put door casings on either side of the opening like bread on a piece of cheese in a sandwich. Use a thin door made from the pieces you carefully cut out of the opening, with beveled battens screwed to one side to keep it rigid and to hold the panels together.
A jointer would make this a much easier job, but those are not an easy purchase to make. You might try applying to an industrial arts teacher at a local school. Curiously, specialized hand planes would also make this easier though hand work is increased.
Here is a quick sketch....Sorry I don't have a drafting table set up...I think the boards are a bit warped!...of how to make Feather Edge Paneling. In old houses, especially from the 18th century, these might have been applied as a wall covering, as the paneling horizontally or vertically under the chair rail, or vertically as a true partition wall. We are using slightly thinner wood these days and if a true colonial look is desired, the planks would be better if the surface were planed lengthwise with a slightly curved blade. That is probably impractical for most people today.
The tongue should be nearly a sharp edge, and the tongue should fit loosely into the groove. When the wood expands and contracts, you do not want the swelling tongue to split off part of the plank that it fits into.
1. Start with random width pine planks. I would think that you should use the widest you can lay your hands on. Nothing less than 8 inches up to the widest possible. Do mix the widths, they would have. Keep in mind that the planks must be securely fastened no matter where you apply them as the wider ones will want to warp a bit as they dry.
2. Start by ripping a 1/8 inch deep groove about 2 inches from the edge of the board. Try all these measurements on a scrap before doing it with your good boards.
3. Standing the board on edge, and getting another set of hands to keep it steady, bevel cut from the depth of the groove to the edge of the plank at about the 3/8 to 1/2 inch mark. Build a jig to steady the plank at the correct angle.
4. On the opposite face of the plank, plane down the edge or use the saw again, to form a nearly sharp edge. It may be as little as an inch from the start of the bevel to the edge, as this side is the less decorative side of the panel if it will show at all.
5. Start with the opposite edge of the same boards.
6. On the other edge of the board, use a quarter inch bead router blade to cut a bead the entire length of the plank. Clamp a few boards together to form a flatter surface for the router to ride on, just to keep it steady. Notice the detail in the drawing even if it is amateurish. That is the correct profile, though others did appear and would look just as nice if not trying to be historically correct.
7. Stand the board on edge again, and rip a 1/4 inch deep groove in the edge of the plank with one pass on the saw. you may also run the groove at just a bit off the mark, then turn the plank around to run it through from the other direction to get it slightly wider. NOTE...Do all of the boards you intend to use at once. You do not want to be trying to reset these angles and widths for more boards and have them look exactly the same.
7. The top of a partition was often not finished at all, just nailed to the unseen side of a beam, but you may secure them the same way at the top and bottom if you like, and even finish them off with crown moulding and baseboards. Nail a simple moulding to the floor, following the line of the intended partition. You could use any moulding you like, keeping in mind that you will be washing floors, banging a mop against them etc. Half round will do, a simple ogee or shoe moulding...whatever you like. Secure to the floor with finish nails, or use reproduction cut nails. With cut nails, you must pre-drill the holes, and perhaps wiggle the drill bit along the length of the grain so the hole is oblong at the surface, and the wide part of the nail must follow the grain of the wood if it is not to split the moulding. Space them closely together as this will strengthen the wall. Stand the planks up from ceiling to floor against the first moulding, making sure the tongues are engaged into the grooves. Place and nail the second moulding, baseboard etc. on the opposite side.
If you have cut the groove properly, the inside or less decorative side will be almost flush, with just a bit of the bevel showing that leads into the groove.
Correct fit and two variations.
These walls were almost never raw wood or stained etc. They were almost always painted with flat milk paint. However since this is your wall...do as you please. Use wood with a minimum of knots along the worked edges, but they would have ignored a couple of small knots here and there in an average house.
You could also do this in a nice native hardwood if you have the skills...walnut...cherry...birdseye maple? figured hardwoods can be a nightmare to work, so be careful.