I had the same pull to the right, a while back. I replaced everything, calipers, master cylinder, drums, and pads. Nothing that I did helped the pulling to the right. Come to find out, it was my power steering pump. I replaced it with a new one, and no more pulling to the right or left. Don't ask me how why the pump would do that, cause I still don't know.
Hah - Val, that was quite a while ago and I still recall how you solved it. Every once in a while I try to figure it out but...get I side tracked - or drunk - and lose interest.
To George on this:
I had a brake pull that was caused by the rear brakes. It was unque in that it didn't make the steering wheel turn when I applied the brakes as opposed to ther pulls caused by a sticking caliper. Thats one thing I would try is braking whith no hands on the wheel to see if it turns or if the truck just drifts to the left or right.
You may want to verify both front wheel bearings are set up the same if you think your problem is in the front.
You may also want to make sure the front is aligned properly.
I have a different method to determine whether the drift/pull is related to the rears. It isn't for everyone, but it does work:
Before attempting this, make sure your parking brake system is fully function and that it engages smoothly and evenly on both sides.
To determine if the problem is in the front or rear braking system, what's basically involved is first applying the service (hydraulic) brake pedal, noting the behavior of the truck and then stopping again - this time applying only the e-brakes.
WARNING: Be careful not to inadvertently lock up the wheels when braking with the parking brake, you may not be able to quickly release it.
The brake system should be tested at different vehicle speeds using both light and heavy brake pedal pressure.
Avoid locking the brakes and sliding the tires. Locked brakes and sliding tires do not indicate brake efficiency.
If the condition exists when using the hydraulic brakes - which act on all four wheels - that doesn't really tell you anything. But if it
only occurs when the parking brake is applied (i.e. it persists without the service brake applied), the problem is in the rear system.
To the OP:
When I got the truck it would go down the road maybe a few miles and the brakes would start locking up from them dragging and over heating. Come to find the brake light switch was out of adjustment and not allowing the pedal to fully return. In search of solving the problem the previous owner had put a new master on it, new calipers & pads, and new rubbers.
Since I've had my truck it has never had strong brakes and always pulls to the right when braking. I went through the rears with all new parts, had the front rotors turned and put new pads on them, re bled the entire system and it stopped better, but still not well, and still pulling right. I re bled the entire system again and adjusted the rears so they just barely dragged. Retested the brakes and no difference. frustrated I sped up to about 40-45 and stood on them as hard as I could! The truck pulled hard to the right and would not lock up any of the tires up. Since that HARD stop, the truck now pulls to the left when braking.
If you do decide to conduct the front/rear tests described above - and it is determined that the rears are the cause, here are a couple of things to check that are often overlooked. I see you have recently gone through them so I won't mention worn/loose/mis-adjusted parts :
1. BACKING-PLATE INSPECTION
Contact Pads - Clean the contact pads thoroughly and verify they are not burred or grooved. Burrs may be removed with very light sanding. If the contact pads are grooved the backing-plate should be replaced.
NOTE: Grooved contact pads may cause the rear brakes to drag or stick. If you attempt to remove the grooves by grinding or filing, the new shoes/linings will not line up correctly with the drum. This may result in the problems noted above.
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The contact pads should be coated with a high temperature silicone lubricant prior to reinstalling the shoes/linings.
Mounting Bolts - Verify the mounting bolts are secure. A loose backing-plate will cause the rear brakes to be very sensitive or grabby.
Shoes/Linings incorrectly installed.
I think this one causes way more braking problems than the backing plate/contact pad issues and it happens more often than people think. I can vouch for that. I am not saying your problem is due to this but it is worth mentioning:
About 20 years ago I purchased a beautiful K20 - Sierra Classic black on black and entirely stock:
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I always do my own work - including brake jobs - and was sure I was doing them correctly. But it had a big problem. With even the slightest rain or humidity, the first couple of stops of the morning were murder. The brakes would lock up and the truck would shudder and shake like it had epilepsy. I pulled the load compensating valve, rebuilt them over and over - and that had no effect. It was like ABS on steroids.
Finally I actually took the time to read the service manual and that's when I found out that I wasn't doing them right at all- I had been installing the shoes in random positions - pretty much whichever one came out of the box first went wherever was nearest.
Each side should have a leading and trailing shoe. The lining surface on the trailing shoe will be slightly larger than the lining surface on the leading shoe. The trailing shoes should be installed in the rear position on each side, while the leading shoes are installed in the front position on each side. If the shoe positions are reversed, the braking performance will be very grabby and prone to wheel lockup.
What to check:
1. Leading and trailing shoes are reversed.
2. Both leading shoes are installed on one side while both trailing shoes are installed on the other side.
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Top:
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Bottom:
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. In search of solving the problem the previous owner had put a new master on it, new calipers & pads, and new rubbers. 
