this is correct. I was in TN about a week ago and ask a DOT officer what the law reads. He informed me that ANY modification from stock was illegal. I asked him if that meant that steering components could not be welded and he said all modification is illegal. I am not a rocket scientist but I am pretty sure that cutting out an IFS rig with rack and pinion steering and replacing it with a solid axel and crossover steering would qualify as modification of the steering.
This same officer also told me that unless you were doing something stupid that troopers really don't have the time to write you for modification infractions unless you were trying to make their life suck. He also started that you are more likely to get popped by the inspection man and recommended that you find a small rural shop :****: