I dont plan on getting rid of the bike. Have too much time into it. Besides its just a great bike. I hate to give up riding for the summer. And cases have been replaced. No numbers. This bike was a basket case when I got it.
Moving to a 05/06 frame will work just fine. I did this very thing last year and its pretty standard.
I bought a yz250 for parts from one guy. Then I bought some other parts from another guy. Lastly, I bought a frame on ebay for $100.
After I switched everything over, I walked into DMV and told them that I wanted to register a bike that I had built from parts. They checked the VIN number, and it was good. I then filled out a standard DMV form explaining where I got the parts from.
I had a green sticker for the bike 30 mins later. I only had to take the bike to DMV so they could verify the VIN and the engine serial number. They need to see it before the will register it.
This is a normal dmv process. It does not matter what the engine serial number is, its the VIN on the frame that matters.