I myself am old enough to have actually watched Bonanza, albeit only in re-runs. The local television station aired it right after Star Trek (The Original Season, long before we had to qualify it with "TOS" - it was just plain old Star Trek then) every weekday afternoon. And I do remember watching it half because of the horses (and half because I was too lazy to change the channel). Oddly enough, this was at the age when my Breyer mania was at its height. So maybe it isn't the worst choice for a crossover after all!
Ben Cartwright's "Buck" uses the Black Beauty mold, which was sculpted by Chris Hess in 1979. This is one of the few molds that I have to admit I genuinely dislike. Something about the pose is more "spastic" than "action packed," and the slight flex at the knee of his front left leg is at least six different kinds of wrong.
The thing about Black Beauty is that he was never described as being a particular breed of horse. Back in Victorian times, with a few exceptions (such as Arabians) you pretty much just had "horses." The concept of a horse as being the member of a breed is a relatively new construction. Thus, you simply have Black Beauty being described as "a horse."
This leads to some oddness with the various models and depictions. In most cases he is depicted as being similar to a thoroughbred, and such is the case with Chris Hess' model for Breyer. Of course, he has been portrayed by real horses of real breeds in the movies, which is why some people assert that Black Beauty was an American Saddlebred named Highland Dale, or an American Quarterhorse named Doc's Keeping Time.
At any rate, back to Buck. Buck was the ripe old age of 12 when Bonanza began, and downright geriatric by the time the show ended. When Bonanza was canceled in 1973, Lorne Greene purchased Buck from the studio's stable, and donated him to a riding camp for disabled children. Buck lived out the rest of his life as a therapeutic riding horse, until he finally passed away in 1992 at the remarkable age of 45.
The real Buck was a Buckskin horse, which is a breed as well as a coat color. Some believe that the Buckskin originated from the Sorraia, a Spanish landrace breed which is noted for its toughness, small stature, and "easy keeping," as well as for its common buckskin coat color.
Although buckskins and dun horses appear to be similar in color, their colors actually arise from an entirely different genetic makeup. Buckskins are the effect of the cream dilution gene on a bay horse, whereas duns are the effect of the dun dilution gene.