The stock 4bbl and 2bbl intakes are pretty similar and neither could be considered a high performance piece so that's partly why I don't think a 4bbl swap is really necessary to get more power. Once the cam is changed the carb would have to be rejetted for sure, new valve springs would certainly be a good idea on an engine with some milage but they're not absolutely necessary if the current ones have low miles. The cam mentioned is bigger than a stock cam but it's still well within the capacity of the stock springs.