New pump is part of the $15 carburetor "kit". But don't do this unless you test it and it's bad.

Turn the engine off and wait for it to cool down. Look down the carb and open the throttle. You should see a steady thin stream of fuel. If it is intermitten the pump is not working correcly. If it looks good don't try to rebuild the carb.

Most problem like this with automatics are the vacuum leaks, not the distributor or carburetor hardware.

But to be sure, check the dwell angle first, it is quick and simple. If the dwell is wrong fix that.