Yup. My catted MRT H is a bit louder - only in good ways - than the factory H. "Good" in that there's no drone, no "blatting" or raspiness... Just a bit more emphasis on the classic "musclecar" tones.
Probably not by much, if at all. A shorter gear will help you launch without bogging by giving the 281 a bit of help down low where its torque is a bit wanting. But you're not putting any more power to the ground which is what really matters in 1/4 mile runs. If you drive it right, you might reduce your 60ft times and that savings might be translated all the way to the traps. I'd wager you'll see a tenth or two reduction but the same trap speed.