PC Is there a way to go into the files and alter the direction the Evils spread in once the Wall of Flesh is defeated?

[The Grimwar]

It's just that after spending ages in this Terraria World, building immense amounts of infrastructure, the fact of the matter is that the Corruption and Hallow always go to the wrong places. And it's only recently that I learned that it's not randomized which direction they go anymore, but determined by some value created at world generation?

I just need to know where that value is in the save file, and how to switch it around so that the Hallow goes East and the Corruption goes West, thanks.