draging and locking up front left caliper

So i have a 02 dak 2wd 9inch drum replaced the calipers, rotors, flex hose, master cylinder, and bled the system,yetstill locks up. Even replaced the drums, wheel cylinders, hardware, and shoes in the back. What could it be, im going to replace the steel line and union going to the front left wheel since thats the only thing left. This is so frustrating, how can you have brake issues, esp after you replace everything. its only the front left caliper