I don't know about all the other questions about fit but I will answer #2. There has never been a "Super Commando" 273
and all 273 manifolds are the same whether 2 or 4 barrel for early A bodies.
I added "for early A bodies to my response to clarify.
#2465769 64-68 A&B body 273&318 LA Right hand
#2465847 64-66 A body 273 Left hand
#2780945 67-69 A body 273&318 LA Left hand
#2843953 67-72 A,B,&C 273&318LA Right hand
