Rear tire width requirements in relation to HP?

I got these cuz theyre sweeeeeet!

I have'em on all 4 corners of my '79 Magnum. 245/60/15.

To address your tire size question, which has mostly been answered, there is no real direct formula for tire width/height vis HP &/or TQ output. As Larry Shepard once put it, on a drag car, the wide tire is only good and used for launch and to a lesser degree, the two shifts of the transmission during the race. Otherwise, it's just along for the ride. A wide tire just becomes resistance. Wind and rolling.

Cars with a narrow tire and big output engines are not putting the hammer down hard on launch but simply and gradually getting into the throttle. The things that aid a smaller tire besides a light pedal are the same for the drag racer. Weight transference on to the rear wheels and overall weight of the car.