Well I finally got them out. I ended up having to do everything at once to get them to budge. I drilled/taped them for a 1/2 bolt, and used that along with some 3/8 chain and chain binder run across the frame to pull on them. At the same time, I rigged up a pickle fork/air hammer with some ratchet straps and bungee cords to vibrate everything. I also heated the socket, then dunked the exposed bushing end into some dry ice & rubbing alcohol. Finally, I beat on the threaded end with a 3/4 steel rod and a 15 pound hammer. Even with all that going at the same time, it still took 5 solid smacks with the hammer to finally get them to pop out. Looking at the bushings and sockets, they look immaculate and smooth; not sure what could have been holding them in so tightly.