K member 73 Duster 318

If your frame rail is that bad in that spot-- I would check the rest of the rails-- both sides- then buy a nice used piece from a member on FABO or source one locally & weld in a replacement section or rail depending the condition of your ride.

that is so rusted it pulled the captured nut section out of the frame rail, I've had some rusty cars but never seen that-- was your car flooded at some point?

Time to jack it up & thoroughly check all the frame support sections front to rear, Lawrence

if that is all that is bad then you will need to figure out how to repair just that section