Reply to "Suggestions for chassis stiffening kits?"

My car is still with it's original paint. The typical pantera cracks at the pillars were there when I bought it and continued to grow over time. I measured their growth which doubled in size after 5 years of active hard driving. I would touch up these cracks and watch them reappear. After installing the stiffener kit they stopped growing. I did the same touchups. Ten years later they have not reappeared.

I drove behind my car and looked at the gap between the edges of the rear deck and the rear face. This would go from 1/4" to 3/4" as my son drove around slowly. Crazy! I thought it was the deck flexing.

After installing the stiffener kit I did the dame thing. No changes in the gap. It was the chassis flexing. Not the deck. These chassis are 35 yrs old!
Plus we've added about 150 HP, better suspension and about 2" more footprint to our tires.