The difference in HP rating results from the different pumps from sea level and high altitude models. The high altitude pump reduces fuel delivery for the reduced oxygen environment of higher elevations and produces less power as a result. This mod is required on NA engines to keep from producing damaging EGT. Can't help you on the axle, often it is stamped on a tag on the differential itself, otherwise I think its on the door jamb not the actual VIN code. Don't know what they all mean. Good luck,
J.D.