my experience with wheel weight has be mixed at best ... if you can score some, remember that it may well be alloyed with aluminum, so watch that it's soft ... i have never been able to find dive weights, but i understand that they're usually pure lead or close to it.
i would avoid battery lead because it contains God-knows-what and if often full of dangerous other metals ... just one guy's opinion ...
i have used range lead, which is usually soft enough for roundball, although you will need to remelt it and get rid of the dirt and miscellaneous funk.
when you cast, do so out doors, and if there's a breeze, you want it blowing the fumes away from you. wear a long sleeved shirt, long pants and closed toed shoes or boots... get yourself some heavy leather gloves as well. You should also wear a hat or a bandana to keep any sweat from accidentally dripping into the melted lead ... it will splash over and splatter and you don't want molten lead on you.
best of luck!