It is common to swap parts to test them so one could easily make a reasonable case for doing so and not get penalized. The ones that will raise flags are the dash, matching VINs in the cluster and PCM, and the one on the frame. Law Enforcement at the traffic stop level only cares typically about the dash and door jamb matching and being present. Law Enforcement at the inspection level and US Entry are a different story.
We helped a guy who was a US citizen who lived in Mexico for awhile and wanted to bring the TJ home that he bought down there. The conversion to US miles instead of kilometers was painful and it took him about a year to get it done jumping through a bunch of hoops.
