Well----if you really think that it is #7, you could check the condition of the valve stem seal on the intake valve--the amount of
oil usage you speak of is about right for a bad or damaged seal. You said you had stock heads, what is the condition of your guides and what stem clearance do you have? You can change the valve seal with the head on the engine
Also check the torgue of the manifold bolts, and visually check condition of manifold around the push rod holes on #7
Jerry