1994 Ranger should have two brake lines out of the Master Cylinder one for the front and one for the rear so Proportioning Valve is in the master.
The front brakes get 70% of the brake pressure, the rear 30%
If you have replaced the caliper' flexible brake lines then the only thing left is a bad Power Booster.
Inside the cab on the power booster is an "atmosphere valve", when you apply pressure to brake pedal this valve opens and lets the 15psi of air pressure in which "boosts" your foot pressure since power booster has -15psi pressure created by engine vacuum.
There is also a spring inside the power booster to return valve and push rod to "normal" position when your foot is off the brake.
Valve or springs can fail which won't let master release pressure to brakes, you feel it more on the front because or the 70/30 proportioning.
To test this, after front brakes are locked or dragging shut off engine slightly push down on brake pedal 5 times, this will remove the vacuum on the power booster, or just remove the power booster's hose and check valve, have to take out the check valve or vacuum won't be released.
See if brakes are released now, if so replace power booster.
Now a long shot is something in the main front brake line that is acting like a valve, so pressure can go into calipers but can't be release when brake pedal is.
Basically you will need to do a "Fluid exchange".
I assume there is new brake fluid in the new master, so start at the drivers side wheel(closest) and bleed caliper until clean clear fluid is coming out.
Then do the same on drivers side.
This will clear the lines of any debris.