Great idea. Wish I had had a couple of water pump cores lying around when I was doing mine.
Here's a way to reinforce the top and bottom round rails of the tailgate. I took 3/4 galvanized pipe, cut it to length and it was a drive-fit into the top and bottom rails of the stock Stude tailgate. Driving in the pipe actually straightened the slight kinks and dents in mine. I then welded solid caps of 1/8" steel to cover the ends of the pipe. The tailgate now feels twice as strong as stock. I'm not afraid to stand on it when loading or unloading.