replacing all vacuum lines under the hood

This weekend I plan to replace all the vacuum lines under the hood. Does anyone happen to know what size or sizes I need to buy and how much. The car is a 72 dart w/ac and a slant six. I don't want to remove anything until I'm ready to replace. Also is it worth it to buy silicone vacuum hoses or just replace them with the standard rubber. And my apologies if this isn't the correct place to post.