That depends on the year/engine/model of the Ranger.
For many years prior to 2010, Rangers have come from the factory with either 9" or 10" rear drums depending on other equipment. The 9" are commonly found on 2WD reg cab with smaller engines. 4x4's, supercabs and/or 4.0's usually get the upgrade to 10". The complete 10" brakes are generally a direct bolt on replacement for the 9" (except the 10"ers from the hard to find 31-spline FX4/Level II axles - dfferent backing plate hole pattern).
2003 FX4 Level II, Supercharged 5.0L V8, Headers, Duals
BW4406 manual transfer case, Aussie Locker, Torsen L/S, 4.10's
Bilstein 7100 rezzies, Cadillac/Mustang rear discs, Duff traction bars
Keypad Entry, Lock LEDs, ABS switch, sway bar discos
Heated seats, Explorer EATC, Trip Computer and consoles
2003 XLT 2.3L M5OD-R1 reg cab beater, 2011 Taurus SEL, 2016 C-MAX Energi Plug-in Hybrid