I use an intranasal vaccine for IBR, PI2, and BRSV as soon as I get the calves home. This can be at a day old or several weeks old. We buy beef calves from a couple of sources, as well as from the sale barn when we have to, so one never knows what they have been exposed to. I agree with the blackleg/clostridial vaccine, its always the best doing calf that has a problem with 'overeating disease'.
I keep the calves in a couple of barn lots and the cows go to pasture. The cows come up 2x a day for feed and I let the calves nurse. I have grafted calves onto the cows in the past but have had trouble getting the nurse cows bred back when I do that because the calves get them sucked down too much. That being said I have two jersey heifers now that are raising calves that way, if I don't see them cycling in a few weeks I will start separating them like I stated above.
Nurse cows are an enjoyable way to raise calves but I don't know how profitable they are with the prices calves are bringing now.
I like a nurse cow that will raise 2 calves without much grain better than one that will raise 4 and requires a 5 gallon bucket! Good luck.