The majority of the rail in that picture will have to be removed and "patched". But that's going to be at least a 3 sided patch that's a good 8" or more long.
That rail is not structurally safe as it is in my opinion. There's very little strength there, and that's right where it ties in to the end of the rocker panel.
Also worth noting, a unibody with significant floor pan damage is not structurally safe either, because the floor pan is a significant structural component. That section of floor pan is GONE, so, just on that the car isn't what I would consider structurally sound. The combination of the floor damage and the frame rail damage makes it a no-brainer, that's not a car you should be driving regularly, if at all.
