This horse has been beat to death on every Mopar forum there is and then some. Its always "this should be illegal, this should be banned, these people should burn in hell, etc.."
This scenario is always the same, someone "builds" a car from a fender tag and makes bank on it. Well first off, you would need at a minimum a title and VIN tag (or perhaps the just the title as some states will issue a VIN tag). Big money cars (read hemi, wing, etc) generally have complete documentation provenance, etc. to prove they are what they are, so someone all a sudden popping up with some rare car with none the stamps, a state issued VIN, etc. isn't going to do all that well.
It is true that a fender tag can legitimize options on a car making it somewhat more valuable than it would be otherwise (N96, 4 spd, etc), however I would submit that if that car has what that tag says it should have then it is what it is. Unless you knew the car previously or someone else did that could accurately prove it did not come with those options that its all a wash. In other words, if the tag reflects what the car has or is then it is what it is. The VIN specifies the engine so you are not making any Hemi or 6 pack car, it also specifies the model so you are not making any RTs, TAs, AARs, etc. At the end of the day you are talking about options.
I do not see anything wrong with replacement tags and you might be surprised how many big money cars are wearing reproduction tags. I am not saying anyone added any options but then again who knows.
The fact is that this hobby has made this an issue, back in the day no one gave a **** about the tags and in most cases couldn't read them anyway. They bought and sold cars based on what they were and what you could see. No one gave 2 craps if the 4 speed poking up through the floor was there originally or not, so long as it worked and was not a hack job.
Its the money people who made the tags a big deal and the idea was developed that the tag meant something, something important so now everyone wants or needs a tag so that they are not shunned by the community. This is natural and like or not there are services to reproduce tags as it is not illegal nor should it be.
I know that hate that is coming as I have said this same thing on numerous other forums over the years and I have heard all of the arguments, none of which hold water. The point is this, if you were buying a car (or bought one) which had a tag that was correctly reflected by what was on/in the car how would you ever know that it wasn't born that way? Even if you did know or find out, so freaking what it has it now. This is why I don't do restos or any of that crap, way too much drama (doesn't mean I cannot have an opinion).