In this penultimate Walk Thoughts post, I had wanted to present you with a route map that I had cobbled together myself, but having now seen the enormousness of the task, I find myself asking: Why reinvent the wheel? The route's already been mapped! I had a reader or two ask me to provide a map of my route, but as I said in the comments, I had already provided such a map at the very beginning—here, in fact. And in that post was a link to this map. If you look at that map and follow the longest yellow line from Gwangnaru Jajeongeo Gongweon (fifth dot from the left if you start all the way at Incheon and can't read hangeul) all the way down to Busan, you'll be tracing the route I took.
Sorry not to provide you with my own graphic, but creating such an image would be a long and very tedious process—not to mention unnecessary, since the Gukto Jongju route I took has been mapped out several times over.
UPDATE: this site confirms that the Seoul-Busan portion of the Gukto Jongju is 550 km. The motel guy in Busan initially thought my hike was only 400-something kilometers, but the entire Nakdong River trail alone is nearly 400 km (if you count the spur leading out to Andong Dam; without the spur, the Nakdong trail is a bit under 300 km).