Here is an eariler thread on what may be a similar issue.
https://www.fordbarn.com/forum/showthread.php?t=167860
Note that the fuel tanks are different, earlier cars vs the later ones, and model to model.
Mine is a 29, the tank and upper firewall are one assembly. Take the tank out, you get the upper portion of the firewall along with it.
What I did was make a backing plate larger than the hole, a "plug" plate that was a tight fit in the hole, bonded the two together using panel bonding adhesive, then fitted that assembly in from the back/tank side and bonded it in place with the panel bonding adhesive. A new repop radiator support rod bracket was installed and it works fine.