I agree it feels like air in the system.
The MC seems to be good since it's "mushy" and not "creeping" to the floor and pumping doesn't seem to make a difference. The MC is 1-1/16" bore OEM which is what I removed originally.
Since I just got home from work I'll hit it later today. I'll start again with bleeding the MC, this time I'll attempt "bench bleeding" with it installed and go from there down.

This really has me frustrated. Been working on my own and others cars/trucks/SUVs for over 30 years. Worked as a GM tech at a dealer for 4 years from '99-'03 and I have NEVER taken a car to a shop for repairs, thought I never would but this one has got me stumped.

What is everyone's thoughts on Vacuum Bleeders? I've bled dozens of brake systems and never needed one, this may be the first.

Thanks to all those that have taken the time to reply, I do appreciate it.
BTW the truck has it's name now "FUBAR".

 

im no expert on brakes but my wifes 96 dakota is doing the same thing ( currently in the shop for other items so i cant work on it) but if you hit the brakes the rears howl to high hell, yet the fronts cant even lock up in gravel.... i was thinking in my situation ( maybe help in yours) is could the lines be crossed on the master cylinder causing a lack of pressure to go to the front and instead going to the rears ( i really dont know if switching the lines could or would make a difference) plus i know you have been working on vehicles for 30+ years so i doubt you made a mistake like that... just my 2 cents, hopefully if nothing else it gives everyone something to ponder lol

 

I wish it could be that, but it isn't. The front and rear lines have different size fittings.

 

OK, finished the bleeding. Very carefully and completely. No difference.

Could the RABS be causing this problem. I know it works by relieving pressure on the rear brakes. Could it be removing too much?

Exactly how do I disable it? Is there a way to disable it in place?
Found it: https://www.ford-trucks.com/forums/8...ml#post7938906