I've seen a technique to change the rotation of the leg in its socket. It involves making a fixture, attached to the leg below the socket that will align the drill bit with the hole in the leg. Sectioned tubing (basically a bent oval or disc) is welded over the original holes in the socket. Then the leg is reinserted and rotated to proper alignment/depth, and the new holes are drilled in the welded-on patches using the fixture. A longer bolt is required because of the extra thickness of the patches.
I suppose the fixture could be eliminated if you slot the holes in the socket, assemble the leg/patches into/onto the socket with the longer bolt, and tack weld the patches to the socket. Remove the leg and finish the weld.