OK, here we go.
I will start by saying that I likely know more about V.I.N. law than anyone on this site. Having been in the car business for many years, previously owning a body shop and having seen about every senario you can think of when it comes to stolen cars etc. I can tell you that it is NOT illegal to have a factory appearing V.I.N. tag made. However, it is not an easy thing to have done. The only maker (other than possibly someone hand-making them in their basement illegally) for these V.I.N. tags takes it very seriously and requires the proper state documents before he will consider it.
All of this being said, each state has their own requirements and it depends on the ownership chain of the vehicle. Some state simply don't allow for an original looking tag to be made period. Other states allow it, and still others it is a grey area.
The reason for my first post in this thread was to alert the OP that before he does ANYTHING he needs to find out if the car's V.I.N. has ever been reported stolen. If not this does not mean that the V.I.N. will never show up on another car some day. Here is a possibility:
Lets say that the subject car in this post is a 1969 R/T, (as the OP has not disclosed what the car is) he knows the full V.I.N. as the title is still with the car. Lets say that whoever removed the V.I.N. did so with the intentions of re-tagging another car. If so, the guy apparently doesn't understand that there are hidden numbers on these cars. This guy re-tags another car gets a title and is driving it. A new title is not much of a problem to get on an old car like this. So, lets say that the OP gets a new original appearing V.I.N. for this subject car. Now we have TWO cars with the same V.I.N. but maybe in different states. Years later ONE of these cars gets stolen and the V.I.N. is now on the stolen car list Nationally. Still later the guy that re-tagged the car with the original V.I.N. gets pulled over for speeding and the cops computer shows the car to be stolen. This is where **** gets deep. The OP with the original car, original title, matching hidden numbers and paperwork to back up the right to have the original appearing tag made is in the clear. The guy that re-tagged the car is in deep do-do. It is a Federal offense because the original car STILL exists and he removed the V.I.N. from the car and placed it on another car.
Now, if you are following all of this you also need to understand that if the guy that originally removed the tag from the car and re-tagged the other car had LEGALLY OWNED both the cars involved then he has the legal right to switch the tags for repair or restoration purposes. The original title has to go with the tag. The car that he removed the tag from has to be junked along with the tag and the title to the one that he re-tagged has to go back to the state as a "junked car." This exception to the V.I.N. tampering law was created because wreck rebuilders do this all the time by buying two like cars such as one with rear damage and one with front damage and they graft the two cars togather as one. ONE car has to "die." It is up to the wreck rebuilder to decide which one. Some state have strickter policies than others on this matter and sometimes a police officer has to be present when the tags are switched or the parts are changed. Most simply want to see that the paperwork is done correctly and ONE car is crushed. There is nothing in the Federal law regarding this being done by an individual or a licensed wreck rebuilder but some state do have an exception for licensed shops only.
Now, back to the grey area. Most states as a matter of simplicity IF they know of the situation will simply slap a "state issued" V.I.N. tag on the car in question and a control number will be issued at the same time that will go in the state title file for the car and it will remain with the car for the rest of it's life. The state doesn't care that it will DRAMTICALLY impact the value of the car. Sooooo, anyone that this concerns will NOT involve the state officials in this matter other than to find a police officer to sign off on the required paperwork to have the original appearing V.I.N. tag. The problem is that you may find a cop that says "no, you need to have a state issued V.I.N. tag installed" and may halt the entire process. Some states allow for a licensed attorney to fill out the state forms for this situation.
You certainly have to make sure you do all of this in the correct order so you don't end up in trouble over this.
How do I know so many specifics about all of this? Years ago I owned a 1966 Corvette that was stolen and recovered within the same week. When they found the car the theives had ripped the V.I.N. tag from the car and destroyed it. I did the investigation to find the guy that makes the original appearing tags and got the correct state paperwork signed off on by the arresting officer that recovered my stolen car in order to have the tag made.
The bottom line regarding this subject car in this post is that it likely is not worth the time, trouble and possible problems it may cause.