I've never seen one on a nailhead yet, but I know that it was california only in '66. That's why '66 aluminum rocker covers have the dimple on the left side. Functionally all you need to do is remove the belt to remove the drag from the engine. Depending on how far you want to go with it, take it out, remove the brackets and vacuum hose. You would also have to plug the holes on the exhaust manifolds. On the later ones you could just use 1/4" pipe plugs, but since I have never seen one like yours, I can only assume that it's similar. For what it's worth, I hope this helps you.:Smarty:
