For numbers sakes.
Dodge Challenger 3.5L V6 = 250bhp, 250tq, 3720lbs
Ford Mustang 4.0L V6 = 210bhp, 240tq, 3350lbs
Chevy Camaro 3.6L V6 = 300bhp, 270tq, 3741lbs
Maybe the Mustang isn't so underpowered in its base model eh? Being 400lbs heavier the Camaro V6 might not be as fast as we think. The Challenger V6 is at best going to be mediocre. Yes Ford needs more power from its V6 Mustang but the lighter weight actually helps it here. The V6 Mustang is quite spritely actually and makes a pleasant noise for a V6.