The R7 axle code (8.8, 4.10, L/S) is used for 28-spline and 31-spline axle assemblies. Your friend's 2001 truck came from the factory with a 28, though. The 31-spline was not available on a Ranger before 2002 model year and then only on the FX4.
Look for the Plastic tag on the housing. I have a few FX4 Level II axles. The early ones with the "bad" Torsen are V305C. My later one (2005) is V313L. These are the true 31 Spline heavy duty axles. These are the only Ranger with 31 spline axles.
Easy to tell by looking at them, the actual housing tubes are ~1/2" larger in diameter similar to F150 and Explorer. They also have the larger axle bearings and brake mounting flanges.
Not sure. I know the only codes I have seen on FX4 LII trucks are V305 or V313. Not sure what the last number identifies. V305C was the original for 2002 with the Torsens that cracked when abused. Then changed to V313.