Why was 440 not a Road Runner option?

Dartnut said
You beat me to it!
As a matter of fact, my brother owned a U code 440 4bbl '70 SuperBird for a few years back in the mid '80s.

The thread header of

Why was 440 not a Road Runner option?

is still correct too. Since the 440 was standard in the Super Bird, it was not an extra cost option.