Ignition boxes - worth it for the effieciencies

Ran an MSD 6 on my old Ranchero for a while. Chasing a problem I replaced it with the OEM Ford Dura-Spark II module. Wasn't the problem, but no difference in cold starting, fuel mileage, or power. The MSD has been in the garage ever since. Prolly ought to put it on CL and get it gone....