After removing the manual hub lock and lock ring, use a small magnet to remove the key from the slot so the nut can turn off. If the hub will not slide out, thread cap screws into the hub body and pull it out. With the rotor off, drive the old lug bolts out from the face toward the back. Insert each new bolt and draw it into place with an old lug nut installed backward, then discard that nut and use a new one.
The owner of a 1988 Ford F-150 4x4 with manual hubs wanted to replace the front lug bolts but could not find the stop screw described in the Haynes manual after removing the hub lock and lock ring. Advice was that the hub should slide out once the lock ring is removed, and that cap screws can be installed in the hub body to pull it if it sticks. Another reply identified the referenced set screw as the key held by the lock ring and said a small magnet can remove it so the nut will turn. The lug bolts were described as part of the rotor and are driven out from the face, then new bolts are drawn in with a reversed old lug nut that is discarded.
