Tried both links, but didn't see the rubber floor covering. Both sites could benefit from improvement with navigation & parts lists, if I might say so.
Went to ACC's site, and they do mention it vaguely in "flooring material", though not by application when I typed in 68 Road Runner.
The rubber flooring didn't fit all that well from the factory, judging by a '68 RR & a Dart I had decades ago.
But in a way, they were a pretty cool feature for the "this is the really base model" look !