Several companies on that list didn’t exist in 1955.
Lockheed and Martin Marietta merged in 1995.
Navistar was created in 1986 from what was left after most of the International Harvester assets were sold off to other companies.
What is now AT&T is the Southwestern Bell division of the old pre-breakup AT&T. They acquired some of the other old divisions of the old AT&T, but others are now known as Verizon while Bell Labs became Lucent which was taken over by Acatel which was taken over by Nokia.
There may be others.
On the other hand, the list came out just in time for Monsanto (which isn’t really Monsanto - it was gobbled up in about 1999 by Pharmacia.) The current Monsanto (created out of Pharmacia assets) is going to disappear again in a few months.
What is now at&t is the Southwestern Bell division of the old pre-breakup AT&T.