Maybe it used to be that if the President and the VP were both killed, or died .. the Speaker of the House would assume the head of the government.
Maybe that’s what I was thinking ..??
You are correct and that would still apply today. The 25th was ratified in the 1960s I believe.
It provided for a new VP to be named and approved by the House and Senate if the President
was replaced by the VP. Before then no procedure was in placed to provide for a new VP
should he be elevated.