Games made with 1.39 version of Twine conflicting with 1.4?

I wanna get ahead on my Twining, and right now that means upgrading to the latest version of Twine. But the last version I was using was 1.3.5; will the latest version conflict with the games (well, game) that I’m already working on? I’m not using anything fancy, just a <> macro fix found in this thread. If there does turn out to be some sort of conflict, how much of a pain will working with both versions be?

If that’s all you’re using as far as custom scripts, you probably won’t have much trouble converting - in fact, I think all you have to do is delete that script, because 1.4 has a working <> macro. (Though the preferred method is something like “[[Go back|previous()]]”