Well I took a couple of small pieces off the engine and tried with that same nut and the one near it.
Here's the stripped nut I can't get off:
So I thought maybe I could remove the one you can't see here
But that is proving difficult without a ratchet for that size nut, since mine seems to have disappeared and I don't have access to my Dad's tools. A friend of a friend might come by tonight or this weekend, although I'm leaning in favor of a local mechanic I've spoken with that seems like he can offer me a good deal and even do some limited welding work. We'll see what happens.
Perhaps this weekend I can purchase some tools to help accomplish my goals. :)