DOES ANYONE KNOW WHY 1997 4.0 IS 97 ONLY OR IF I CAN USE A DIFFERENT YEAR AND JUST CHANGE SOME PARTS HAVING A HARD TIME FINDING A REPACEMENT ENGINE

 

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Turn off ALL CAPITALS

1990 to 1996 are the same if swapping block and heads together
In 1997 4.0l OHV got a new crank shaft that used an 8 bolt flywheel/flexplate, 1996 and older used a 6 bolt.

But if you are buying engine WITH flywheel/flexplate then any 1990 to 2000 4.0l OHV will be fine to use.

You will need to use your 1997 upper and lower intake with injectors and sensors on any engine you get, or fuel system and wiring won't match up.
Also most likely the oil pan, but have to see on that, I think 2WD and 4WD used different oil pan shapes.
I would also put in a new oil pump and replace rear main seal unless you are getting a new/rebuilt engine.

History of the 4.0l OHV here: Rebuilding The Ford 4.0L Pushrod V6, Doug Anderson, Automotive Rebuilder, April 2001

There were differences over the years in pistons and heads but as long as you are buying/using a long block any year will be fine

And you can always buy a 6 bolt flywheel(manual) or flexplate(automatic) if needed.

 

thanks that's what I needed to know