Like Alan said, if they are original, then heating them to burn the "loc-tite" off helps a lot. I just happen to think of something else. Did you remove the snap rings before you tried removing the bearing caps jbenn? They can be pretty rusty, and hard to see, but they will still prevent you from getting the bearing caps out.
When you put the new u joints in, be sure the hole in the trunion for the grease fitting is facing towards the center of the axle, not the wheel. That way, with the wheels cut all the way, you can screw in the grease fitting, and grease the joint. Then remove the fitting, and install the plug in the hole, that comes with the joints. Then cut the wheels the other way, and do the other side, same thing. If you leave the grease fittings in, they will get sheared off. That's why the axle u joints come with a fitting and a plug.
~Chuck