[rotorwrench]

Most folks change due to getting away from the original carburetor and Load-O-Matic system. Dual point set ups will increase the dwell time for the coil and thus allow for a better spark. As was mentioned, make sure to get the springs & flyweights adjusted for best spark control for the engine application. There will be no benefit for under load spark control but this will only give a lesser amount of fuel mileage overall. If a later modified vacuum advance type distributor such as a GM unit is utilized & properly adjusted then the mileage would be better. Most modern coils function well enough without dual points but it always has some benefit.