Truck pulls to the left when I apply the brakes

1995 Chevrolet C1500 Silverado Ext Cab
5.7L, Auto Transmission, 2 Wheel Drive
182,000 miles

Recently my truck started to pull to the left when I apply the brakes. When I have driven for some time, about three or more miles, the pulling get worst. Panic braking is really dangerous. I first replaced the brake pads and rotors, I also bled the brakes, but problem persisted. I then cycled the ABS by braking hard on a wet surface approximately ten times, hearing the motor buzzing each time. Bled the brakes again, all four wheels. Problem still persisted. I then replaced both front calipers, used the same brake pads (recently installed, 200 miles), and bled brakes, cycled the ABS, bled them again. Pulling to left still persisted. Thinking it may be the brake pads, I then swapped the brake pads from left side to right side, and vice versa, but pulling to the left still remained. Please help.