LLMs are great at producing documentation - ask one "hey can you add a TODO comment about the thing on line 847 that is probably not the best way to do this?" while you're working on the port, and it will craft a reasonably-legible comment about that thing without further thought from you, that will make things easier for the person (possibly future-you) looking at the codebase for improvements to make. Meanwhile, you keep on working on the port that has byte-for-byte identical output.