[Signman]

That move under hard braking is the result of the suspension setup.
When you increase spring rate on the right rear to plant both slicks equally and go straight it loads the opposite corner, the left front then helps load the right rear. When the driver gets on the brakes hard the spring rates on the front are not equal the right front appears to collapse and the car gets upset. Some of that can be tuned out with shock adjustment am sure a good chassis shop can get rid of most of it. my footbrake Chevelle does it, the Tomata Can did it and my IROC-Z has done it.