You will not be able to determine which gaskets you need until you see which ones failed - and then you will need the old gaskets as the 351 W used multiple (6 or 7) different configurations on the water pumps.
You might also want to look at the type of
antifreeze you are using. My Roush engine didn't like Dex-Cool and leaked after a couple of months. Changed the gaskets and it did the same thing again. I called Roush and they suggested changing the
antifreeze. Changed to Motorcraft Premium Gold and no leaks with over 20K miles.
Just offering tips based on what happened to me.
Good luck with your efforts!