For max acceleration you want to spend as much time in the rpm range of max average horsepower.
That high torque 440 with a 2600 stall converter will only be able to deliver the actual hp being made. 500 ft lbs torque only makes 250 hp at 2600 rpm. At 4000 rpm the 500 ft lbs has climbed to 400 hp. If the motor makes 500 hp at 5200 rpm, and the motor will still make 500 hp at 6200 rpm you have the full 500 hp average, minus efficiency loss, if you have a 5200 stall converter, average power delivered will be highest. Stall torque ratio and overall efficiency can skew the actual best stall speed.
