I recently had to cut some drums off a '53 rear end. I used a cutting wheel on my 4.5" grinder (they are slimmer than the regular grinding wheel). You'll want to cut across the outer wide part first...you can see the backing plate and you should avoid it. As you come towards the middle, be aware that there is a flange holding the studs, and the drum is right up against it. You do not want to cut into this flange, so stop as you get to within 2" of a stud. Also, mind the depth of your blade; keep it just deep enough to cut the outer drum shell. Make 2 or three more cuts like this around the drum, and then whack it hard with a mall or wedge a big chisle in-between the cuts. It is cast iron and will shatter with just enough persuasion. Be safe and wear eye protection!
Patrick