I bought a used 2000 4wd ranger years ago and the frame was so rusty it fell in half when it was dropped off by the rollback. I spliced on another frame section so thats all good. Shortly after the rear end went out and a friend of mine gave me a rear end from a explorer with the same rear ratio (3.73) . I cut off the spring mounts and welded new ones on top so now I have disk brakes all the way around.
The brakes were bled but never were good so I got a master cylinder from a explorer and installed that. The brakes are somewhat better but not like I would like. I will soon be doing a full bleed when I can get some speedbleeders in here.
Also the brake pedal will not come all the way back on its own so the brakes drag a little until I reach down with my foot and pull the pedal back the last 1/2 inch or so. Is there not supposed to be a pedal return spring ???

 

Brake pedal spring return is inside the Master, should be no spring on the brake pedal itself
Did you adjust the end of the shaft from the booster where it meets the master, if should just touch the masters piston when master is in place
But brakes shouldn't drag if that was the issue, pedal just wouldn't come all the way up

Was the master new?
If not it may be bad, has a ridge inside that prevents full return or broken/old spring
You can remove it and drain it then pull out the piston and spring
Have a look and see if piston slides smoothly and spring is strong

As far as the braking in general is your 2000 4 wheel ABS or Rear ABS?
The proportioning is different
If RABS you may want to install an adjustable proportioning valve for rear disc brakes and remove the ABS valve unit

 

Ok so I did this also with my 2000 ranger with the rear end from an 02 explorer and I can't seem to find the right brake lines online; what hoses do I need to make this conversion?

 

I just used what was already there on the ranger.