Randy,
That one is a gray area. Technically he should use the date that he registers the car. But every DMV will treat it differently. I would call the DMV he has the appointment with and ask them about that to be on the safe side. Also who is actually putting the car together? They may ask for a 4th receipt from the person who is actually building the car to prove that it wasn't all done by the same people and hence can be called a turn key. I talked to the DMV a couple of years ago about having a car built in Montana and they wanted more than 3 receipts toprove that it wasn'tjust one operation using different people to sign off on stuff. They wanted a receipt from the paint and body shop, one from the interior shop, and one from the person or persons who actually put the car together along with all the others you mentioned.
Ron