Shifting Speeds?

I have a 727, with a 318, Edelbrock Performer Intake and Carb. At what speeds should the tranny shift to second and third. Right now it shifts to 2nd at 20 mph, and 3rd at around 50mph. But if I let off the gas while accelerating at 40 it shifts to 3rd. If I dont let off at 40 it shifts at 50.
I have BP kick down kit installed.

Thanks,