the 2001 mileage is stored in 2 places. Its in the pcm - but that's not displayed and you never see it without a scanner. the mileage thats displayed is stored in the cluster, so if you swap the cluster, you change the displayed mileage.

i just checked the calculator to see what the metric equivalent was.
141,000 mi = 226,000 KM
so its not that you truck had a "canadian moment".