In my opinion if you're sitting on a shipment of parts and you have customers that show a high level of interest, just give it to them first. They make your life easier. You don't have to make outbound calls/texts until you get through the group that wants it really bad. The time they spend canceling appointments is counter productive.
As far as the hardware being synced it's not by VIN the advisor I'm cool with here says they have a part number they take that out of my car's system, then they sync it with the mothership and attach that part to the VIN (edit I assume the VIN has a profile of some sorts with all the part numbers). This has happened for my steering wheel stock that was splitting as well as my 1st run charge port (they said they are on the 5th revision) still pretty awesome considering a legacy automaker would have been on their second revision at best!