Nothing is out of the question if the dedication is there. But the best thing to do is drop all the cross training time waste nonsense and train to box. Being in fighting shape is a different mtter than being in great shape to do anything else. Also, don't be afraid to 'train' yourself; watch tape of great fighters as often as you can because your eyes won't mislead you nearly as badly as many of the people you are apt to encounter 'training' amateur boxers.