A high stall converter will allow the engine to rev higher before it locks up which gets the engine in the desired powerband faster and makes the car accellerate faster.
You match the stall speed of the converter to the application of the vehicle by rpm range and intended use. For instance my Cuda engine develops max torque at 3,500 rpm so if I were only racing it I'd run a 3,500~3,800 converter. Since I mostly street drive it but race occasionally I went with a lower stall converter that stalls at approx. 2,800 so the car is more streetable.
If I understand you right your combo of the 383 and stock converter is sufficient for street use although a little looser converter of about 2,200~2,400 stall would be faster. Really no need to go higher than that. JMHO