In 1957 they meant for you to use a non detergent 30 weight engine oil. Now you use a much better oil: TWC-3. I run my '57 on 1:32 because of it,but I certainly would not try anything leaner than that.
sfure <br /><br />24:1 is 24:1, no matter what oil you use. Just use TCW-3 oil mixed at 24:1 for proper lubrication. The richer mix is to seal up the tolerances in older motors.