Since car titling/registration varies by state, you are going to find kit cars titled as "authentic" rather than replicas. States like California make it somewhat tedious to properly register a kit car (
https://www.dmv.ca.gov/portal/dmv/detail/vr/spcnsreg ) so some people may try to avoid the issues by securing a VIN from a real car to attach to the replica or otherwise present it as an actual vintage vehicle. Other states, especially those that don't issue titles to older cars, will register a car based on very loose standards, by comparison, and they are later sold in a state that will issue a title based on previous registration.
If a kit car has been titled/registered as an authentic vehicle, it becomes a point of honesty by the seller to reveal that fact, and a point of obligation for the buyer to do his homework.
For Marv, once a kit car has been properly titled/registered in Ca., there is no special obstacle for a subsequent buyer to register it he would any other vehicle. The hoop jumping comes with the original builder.