I know I'm reviving an old thread, but I am adding my $0.02 for future people that are actually doing a search.
I did my Explorer swap over 1.5 years ago, and everything went smoothly. I, too, read that the stock Ranger master cylinder will work fine.
I had decent pedal pressure, and I was stopping just fine. Little did I realize that I was only using the front slotted & drilled performance rotors only. I just didn't know any better or how much better it would stop with the Explorer MC.
If in doubt, or you have easy access to the Explorer MC, install it anyways.
I checked my brakes 6 months after the installation, and the brakes looked great. I thought they were being minimally worn.
I checked again recently, and it actually had no additional wear on the rear discs.
Installed the MC, and my truck brakes better now.
I do not have ABS.