My guess is that those vehicles are older than 15 years, then they are exempt. If they are less, then they probably got in under the radar. As I was saying, it all depends if you have a buttmunch approving your entry. I think 99% of any modified vehicle will make it through if the way is smooth with people you know - but all it takes is for some stickler to pull out the "rules" and things could get ugly.