I am getting a vibration in my brake pedal when applying the brakes. It seems the worst when im am traveling down a hill and have to apply the brakes. I can feel it in the pedal only. Steering wheel feels fine and the truck doesnt pull left or right. It feels similar to ABS kicking in.

Truck has 38,xxx on it. I replaced the front pads around 25K with EBC Green stuff 7000 series. They were the heavy duty ones for heavy trucks. Only a 2" level on the front with 305/55/20 Terra Grapplers.

Any thoughts?

 

The rotors could be getting warped. Since you notice going downhills and probably when getting off the highway as well, that is typical for rotors to show signs of them being wapred. They are intense heat applications. They will keep getting worse, but is nothing to be concerned about.
Also, could be your rear rotors as that can happen if you tow/haul regularly.
Brakemotive has drilled/slotted rotors for $220 shipped front and rear w/pads. They have an ad in the vendor section of the classifieds.