I don't background but have raised a lot of calves through that weight range. Seems to me that chopped alfalfa, grass (I assume you mean hay) and ground corn should be sufficient but in the right proportions.

Too much chopped alfalfa along with a lot of corn could lead to health problems. 

A little (limited amount) of each along with a lot of grass hay, maybe free choice could work well but watch the proportions of each. 

Basically, heavy on the grass, lighter on the alfalfa and corn works in my experience.

Good luck