4.0 engine compatability question 03 to 05

[old rock]

Ok, I'm a new Ranger owner. I've had F-150's for what seems like forever.
I recently purchased a 2003 fx4. The trans went out yesterday.
I have found a replacement 2005 from a sport trac. It is a direct fit.
The question is, why is the engine not listed as a direct fit?
My 2003 has 205k miles and the Sport trac has very low miles. I would like to just replace the 2 of them together.
Any input would be greatly appreciated.
I am sure you will be hearing from me a lot in the future. For what it's worth, I do have a ton of mechanical experience.
I am thinking that the diff may be a very minor plug or sensor.
Thanks again.............

 

[06RangerXLT]

not familiar with sport trac, but if its the same motor you can swap over the different parts. Also, make sure your transfer case will bolt up to the output shaft.

 

[old rock]

Ok then. Kinda hoped for a little more input.
The transmission is listed as being the exact same but the motor doesn't come up as the correct replacement. It is ussually somthing minor like posssible the oil pan or some other minor diff.