tires in the old days were a HUGE limiting factor , + gears in the transmissions are lot shorter and more plentiful today , so 260 hp today will do much better lots more than just hp in play
Although I agree to both of what you said, but that was the 04 GT mustangs time with a 4spd auto with 3.27 gears. Thats comparable to a 3spd auto with 3.23-3.55's, which is what the 340 came with from the factory. And as for the tires, that is with todays times I have seen with modern tires.