Removing lower ball joint

If this is a factory ball joint the tip of the taper should have a hex ground on it where you can put a wrench or pair of vice grips to hold the taper while you use a wrench to remove the nut. If that isn't there or it is rotted away you could take a sharp chisel and split the nut on both sides to get it apart. If you have access to a cutting torch you could cut the nut off as well. Once they are free of the seats those are about the only options unless you can get them to stick back enough. Usually the problem there is that any of the lubes or penetrant used to free the nuts make that difficult.