The high base timing numbers are for an HEI, lower numbers for a stock distributor. It has to do with the amount of timing in the distributor. You can try either and figure out what runs best at low and high rpms. Then get the distributor set up to achieve the best of all your testing combined.

Now that the float is set properly, which hopefully you adjusted the height and drop to within the thickness of a piece of paper, the fuel pump should finish up the equation. Not to mention fuel economy should be much better!!!