Based on mph alone, at 3600# you picked up ~55 hp with the head swap. At 0.600" and 0.700" lift the 270's are about 20 cfm better than the 240's, and at 2 hp per cfm you definitely got the HP improvement from the heads. Agree that maybe exhaust or a different induction setup migght get you another tenth or so. If it's full 3" exhaust it's probably a choke point and worth trying cutouts. Again, absolutely beautiful Charger!!