If you are running a bigger cam and a larger carb or multiple carbs then a
centrifugal advance distributor maybe what you need, due to lower intake vacuum . Fuel econ may or may not be effected, but it should be better to tune.
Mallory makes a centrifugal advance distributor. Check on E-Bay there is a guy selling Mallory's for $99.00 I bought one from him. It was new in the box the number is MAL-2363001 I have not had a chance to install it yet, but hopefully I will find the time soon