neutralize that rust on the inner fender and try to find the original glue that was used to stick the front fenders to the body.. I see the jacking holes are gone to hell. In such a case I usually advise to buy replacement grafts complete - its very hard to make those pieces by hand - as they have to strong enough to lift the whole car.
Its also wise to locate replacement door strikers or the little plastic pieces that go inside them. By looking at the rust on A pillar I think that the drains above were seldom cleaned nor were the bonnet hinges lubed. Its a water trap in w123 chassis and those hinges are NLA from MB now. Used ones are very expensive because of the NLA clause.