If you want to be technical about it, you could buy a 440 in a RoadRunner in '70, just you had to choose the SuperBird option (package) which was considered an extra cost option on a '70 RoadRunner and came standard with the 440 4bbl.
That's the only way you could get the 440 4 bbl engine in 1970 on a RoadRunner.
Just like in '69, you couldn't get the 440 6bbl in a standard RoadRunner unless you opted for the A12 option (package).
But............it was technically available, just not in a base car without the package.
So, it was an option.
Technically speaking...............
