How can you tell? Where to look for VIN, or other absolute identifiable features? What years?
I have a 2002 Ranger XLT 4dr but I’m positive it has had an engine swap. Finding different parts that are not Ranger but Sport Trac OE fitments. Thanks for any and all information.

 

The 4.0 SOHC was used in the Explorer first, I think 97
So the parts were in the Explorer first.

Rangers didn't get the 4.0 SOHC until 01

In 2002 there would be no reason for Ford to give the Ranger and the Explorer 4.0 SOHC engines different part numbers for the exact same part.

So it's very possible almost all the parts on a Ranger 4.0 SOHC have exact same part numbers as the earlier Explorer and Sport-Trac 4.0 SOHC

 

2001~2003 RangerXLT\ExtendedCab with V6~4.0L~SOHC + 5r55e Trans + 1354 TCase +... &
2001~2003 SportTrac were near identical twins with same frame & drivetrain.
"LongBlock" fitments were same on both models, as I've learned buying parts for my 2001 SportTracJob2 over the years.
The major differences were of course
RangerXLT had HalfBackSeats & SheetSteel "Standard"6ft Bed.
SportTrac had FullBackSeats & PlasticTub "TwoShort"4ft Bed.
2004+Later Ranger & SportTrac builds had increasing differences.