Howard was brilliant agreed. Other than his age, he truly was one of the best choices.
Gable was untouchable in that role--no one could have topped him, imho.
". (Also Ty taking Scarlett up the steps in that very dynamic scene.)
Read somewhere that he had to carry Vivien Leigh 13 times up those stairs with all the retakes. However, she was very light apparently and it wasn't an exertion for Gable :-).