Body improvement

[NoHachi]

Just improving the mounting places moves the weak points a little further..not much to be gained that way.Having said that:
Strutbraces are always a good idea on older McPherson cars..can have quite an impact.
Foam can be a nice improvement, but at the cost of extra rust sensitivity.

Other then that, there is not a lot you can do without making the car very heavy..Best way of stiffening something is working along the directions of the forces that are imposed on it. That means tubes going through the whole car.