They are both running 347's. The coupe is a flat tappet cam while the GT has a roller cam. 410 hp on the dyno for the coupe, 450 on the dyno for the GT.
The coupe,I call a bad boy in a tux is hard and rough. The GT, a bit more refined,a bit more comfortable, a bit more quiet and perhaps a bit easier to live with. Big brother little brother
Bill