F150/Expedition Brake Bleeding Issue?

Quite a bit of detail, but bear with me. I want to include anything that may affect this - cause frankly I'm stumped.

The vehicles are a 97 Expedition and a 98 F150. Expedition has ABS and four wheel disk. F150 has disk/drum and seems to only have ABS on the back, cause I don't see the typical valve body. Only a block with an electrical connection to the rear line on the master cylinder.

The Expedition blew a brake line. The reservoir was run dry. Line was replaced.

The F150 got a full brake job including new calipers and wheel cylinders. The two rear brake lines were also replaced cause they looked kinda flaky.

My dad and I bled brakes for longer then it took to put 'em on. In both cases we couldn't get the pedal to stiffen. Started the car and did the typical push and release at each bleeder valve. From the farthest away wheel we worked our way around. Must have ran a quart and a half of brake fluid through each vehicle. Get a solid stream of clean fluid, no bubbles. The pedal never stiffened, and we went around multiple times. No leaks or wetness anywhere - we can visually see all parts of the lines.

I've bled brakes before on a bunch of other cars, including an 01 Crown Vic, a 97 F150, and the very same Expedition we worked on. My dad has done this probably more times then he can remember. We've never had this problem.

Any ideas?