Just do what you are comfortable with. USS-64's are darn good machines.
Light up sign, relays, switches and such have a strong part out value.
Creighton
I've owned a CSS, and I'll say it again-I don't think you can ask for a better (original) cooling system, especially in a square top. I'm under the impression the later USS machines aren't quite as well-made as the earlier ones, but still pretty solid nonetheless.
Sadly, the later ones usually do not have the lighted sign, at least not the 64's. The USS have a fluorescent tube light in the bottle door, I'm guessing Cavalier decided that was good enough. Strangely, I've seen a few more later USS-96's with lighted signs. I have no idea why.
I've thought of parting machines out before, but I'm not sure it's something I could handle.
It's so difficult to find one in decent condition for anything approaching a reasonable price. I realize these machines aren't going to be mint, they're at least 30 years old. So far I haven't found one in as good a shape as the CSS was when I bought it, that was priced reasonable.