With a decent feed program, you should be able to finish him by 15-17 months, I would think.
Best cross? It depends. Are you talking slick shear or fitted?
I don't think that the breed is as important as the individuals themselves. I also don't know if there is such a thing as the best cross, especially since the club calf industry is always changing with the type of cattle that win, so the best cross is not always a constant. Right now the trend, I think, is toward smaller, thicker steers. In other words... "tanks". 25 years ago, they wanted large framed cattle. 25 years before that, they wanted "belt buckle cattle". We aren't back to the "belt buckle cattle" & I doubt that we will ever get back to that completely, but I do think that cattle are trending shorter & high corn prices will only continue to cause that trend to continue. Also, different areas of the U.S. are different than others.
With that said, almost every "great" steer has a little Angus blood in it, but a high percentage Angus probably will probably not win a major show. Lowline Angus are typically thicker than the typical "Americanized" Angus, and I personally think that they would be ideal low percentage cross within a cross system. Percentage Maine Anjou is a very common component in many "great" steers. Charolais is becoming quite popular, especially for slick shear shows. Chi, Simmi, Shorthorn are some of the other breeds that are commonly found in winning club calves.