Correct me if I am wrong, Fury I had rubber floor coverings with a hint of interior color spatter..like a taxi or cop car.
Most low line Plymouths (Belvedere,Road Runner,Valiant 100) came rubber floor mats with carpet as an extra cost option.
Your broadcast sheet if you find it when removing the interior will confirm carpet or rubber mat.
Its ok to put carpet in. Tan or black should be fine.
Hope this helps.