Normal body sag?

[rodo]

As one thing gets repaired... Finally getting my hood spring in today, after wrestling out two broken screws from the spring, and as I'm fussing about under the hood I notice that I can see light from a seam where the firewall meets the right fender. Tiny bit of a crack, like the seam has opened up a bit. I know it is not right as the other side, left fender, is tight. Not seen anyone else with this issue. Generally this care (1981) is in pretty clean shape, little rust.) So...not even sure where one would begin with pulling that together. Weld in a patch? Just weld the seam? Both in the engine compartment and the wheelwell? Some other options?