Thanks for all the info.
The truck has a title and was last registered in 2002. I talked to the CA DMV and they are requiring me to take the truck to the closest CHP office and have them do a vin inspection. From there they will see the newer engine not matching the old engine serial. They said the CHP officer will then use the body tag as the Vin#. They called this Blue Tagging? Anyways this seems to be the most logical method,
That seems to be your best bet.
I think the closest California DMV to you is Needles. If the Seller refuses to cover the cost of towing the truck there and back for the blue tag then consider invoking your buyer protection.
It is a challenge to register these truck in Nevada even with all the proper paperwork.