Six pack manifold and carb

I think it looks like the 71 is 77, but that doesn’t make sense. A 71/72 should have 902 heads. 73 up had 346 heads. But they could of been changed at anytime. Also with the strengthening ribs it should be a 74 up engine. Maybe go to 440 source as the have a: everything u wanted to know about 440s page. Kim