Cool stuff! Love to do that sometime.
Something looks wrong with how that Dart handles. Looks like the geometry is messed up, can't see it moving around that much, and picking a front tire up. Chassis seems stiff enough, but it has some real leverage somewhere that throws the car around. Maybe really soft sprung and HUGE sway bars? The Camaro looks right going around a corner, the Dart looks spastic.
Too bad he put it in the ditch, might have won his class with it. The winner broke 2 stages before the end, but had enough of a lead to win. The Dart got second.
Here is another video I found. Looks like the car was build by Dodge and then given to the team to run.
Dodge Secret garage