The stock 273 valve springs are all the same....2bbl and 4bbl. 318's used the same springs too. When installing replacement springs and retainers, check the diameters too, as some will rub the stock adjustable rockers. That's where using some bee hives can be beneficial. As for spring tension, that will depend on the cam and the RPM range you plan on using. If you don't expect to ever go over 6000 RPM, I'd use the stock or weaker springs as they will be a lot easier on the cam and lifters.