Since C4 is not in the main signal path, it has little influence on the tone. Your 330n is closer to the spec value of 390n, but most caps I measure tend to test lower than the stated value. Some may be as much as 20% lower. If you cannot test them, I am sure that either the 470n or the 330n will work. If you have really sensitive ears, you may wish to socket the C4 position and try both of them. I’d wager that you would have a hard time hearing much difference. Don’t be afraid to try. That’s part of the fun.
BTW, welcome to the forum. Please post a photo of your build so we can all see your results.