[Bobboloo]

I've read the California code before and my understanding is that you can build one car from two cars in the fashion you see as fit. You cannot tamper with a VIN i.e. grind it off or re-stamp. That is definitely illegal but there is nothing written about percentages of sheet metal belonging to which VIN etc. It just states that you need to be the owner of both cars that are to be used in the process.

In reading the code it seems to me that theft was the concern when it was written. Forgery didn't seem to be the concern. I'm sure there are laws dealing with forgery in the attempt to defraud one of ones money but doubt they are car specific.

Disclaimer:
I'm not a lawyer so this is not legal advise. I'm just stating how I understood what I read concerning this subject
You should look up the code, read it, and determine for yourself. People are eager to give their two cents on the board but nothing beats getting the info straight from the horses mouth. The horse in this case being the California Vehicle code.

P.S. No chassis should be left intact with it's VIN's missing so you should consider partitioning the bad chassis.