Need a Good Website Calculator for ET to HP

Example.
Guy with a nicely built 408, stock converter, street tires, and 3.23 gears goes to the drags, spins the tires ferociously, bogs when it hooks, and goes 14.50, at 95.
He buys a set of slicks, puts in a quality 3500 stahl converter, doesn't touch the motor!, and goes 13.50 at 105. Did the horsepower change, or did he just make the combo better?
The Calculators have to assume certain things for accuracy. If a guy is running a stick, spinning tires, bogging, missing gears, running out of fuel in high gear, NO calculator can give an accurate number.