I have done it both ways. I used the floor/toe board combo on my 50 daily driver, and used separate floor and toe board pieces on my future museum piece (a guy can dream can't he?). The one piece combo was easier to weld in, just not original. As far as "added support and rigidity" of the factory seam, I respectfully disagree because the original seam is two flanged pieces of sheet metal spot-welded (prone to rust) an inch apart the width of the cab, as opposed to a sturdy bend in a single piece of metal.
