I don't know much about DMVs but if they see a VIN on the floorpan and another pop-riveted to the dashboard, I'd be surprised if they expect matching numbers on the
engine motor.
In the 36hp era the serial number was on a plate behind the spare tire in the front valance. Later it moved to the pan above the shift coupler. I had an early body on a late pan so it had two VIN, but it had already been registered by the VW dealer in McMinnville, OR. I wanted to buy just the floopan (for a fiberglass body) they had on display in their dealership, but by the time I got back they had dropped a 1957 body on it so I bought the whole thing.
I guess the 1957 serial number went when I rat-rodded it.
Body shops can't work on my 1971 SUPERBeetle because it doesn't have enough digits in the VIN.