Rangers got the M5OD-R1 manual 5-speed transmission from 1988 until end of production in 2012
But they came in 2WD and 4WD models, you can swap tail shafts and housing but it is extra work.
They have a integrated bell housing and 3.0l has unique bolt pattern so you do need a trans from a 3.0l
Mechanically you can use any year 1991(Rangers got 3.0l ) to 2012 as direct swap.
So yes, a M5OD-R1 from a 1994 3.0l Ranger will work, but there is a problem.
Computer and Speedometer on your 2003 wants to see OSS(output shaft speed) signal of 32,000 pulses per mile.
1994 trans will have speedo cable and VSS(vehicle speed sensor), VSS only outputs 8,000 pulse per mile(PPM)
Same as the rear axle VSS used until 2000
Not sure if you can swap out tail shaft housing and sensor/tone ring, I would bet you can just never done it or read about it.
So you may be better off rebuilding or finding a 2001 or up M5OD-R1 from a 3.0l 2WD with OSS sensor
One of the issues with M5OD-R1 was the 3 rubber shift rail plugs at the top of trans, they would leak and trans could run dry and burn out.
Good read here on replacing those plugs: http://www.therangerstation.com/tech...ntenance.shtml
Easy to do when trans is out