The line across the centre was primarily caused by the continual wrestling between North's Gary Dempsey and Collingwood's Peter Moore in the 1979 Premliminary Final, though I am not sure that it was the cause of it becoming national via the old NFL. I was at that game, but as a 5 year old, have virtually no memory of the game apart from the area where we sat at VFL Park.
I do remember however that Cornes was far from spectacular, Ebert wasn't too bad and Davies fared OK mainly in the forward pocket - Michael Moncrieff would have been the likely full forward with Davies in one pocket and Leigh Matthews resting in the other when he wasn't on the ball.
Ian Paton was their ruckman and IIRC Davies was rarely (if ever) used in the ruck.