Danny
If you are looking at the VIN on the ownership documents it may have been assigned by the DoT for the state/province where it was first registered. If there is a VW chassis then you find the original VIN on the tunnel between the seats in front of the inspection plate. See this link for decoding the VIN https://www.thesamba.com/vw/archives/info/bugchassisdating.php
If it has 1981 and MiGi it sounds like you’re looking at the kit serial number. I think that’s irrelevant to your registration unless the car’s never been registered before by a state motor vehicle department.
Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica Roadster
If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)