Silence speaks volumes in the Constitution. If no mention then no right to vote. It clearly states:
“If the Congress, within twenty-one days after receipt of the latter written declaration, or, if Congress is not in session, within twenty-one days after Congress is required to assemble, determines by two-thirds vote of both Houses that the President is unable to discharge the powers and duties of his office, the Vice President shall continue to discharge the same as Acting President; otherwise, the President shall resume the powers and duties of his office.”
Ford did not pic a new VP based upon the precedent set by Truman following the death of FDR. I believe as acting president he could have though.
Ford did pick a VP. It was Nelson Rockefeller.
When the VP is serving as Acting President he is still VP, and the Amendment continues to refer to him as such. Because he is still VP, the office of Vice President is not vacant. Therefore no VP can be appointed. Think about it… if serving as Acting President meant he was no longer VP, then when the President resumed his duties the VP would be out of a job.