That is a rather old sketch that does not look much like present day TB's. I can't just show you what a "normal" TB looks like because there are somany different types. Sprinters look more like Quarter Horses, distance horses look more like Akhal-Tekes and turf horses have their own unique appearance. If you had a picture of your horse I could tell you what type he is and what is good and/or bad about his particular conformation as a race horse. When I have time I will post a few pics of the different types I am talking about. They can not be simply explained.
And in my opinion, Secretariat is a bad example of a perfect racehorse comformationally, he just happened to be one of the best racehorses that ever lived. But racehorses sometimes run beyond what their conformation should allow.