Son of seed truck..

So I have a question. I'm wondering what I would have to keep of the 72 in order to keep the title and possibly get a 78 or 79 or late 70s truck in better condition and basically retitle it. Of course not looking to do nothing illegal at all. But how much of it would I have to save? The entire cab? The dash? The doors? Obviously I would want to keep the bird bath Hood and the older Grill either way...