I was fooling with some H body numbers and I figured out the VIN # of the Monza built exactly halfway through the total production of all Monza's..
It would have been a 1978 model, and the last 6 of the vin would be 190,840.. it would have been the 90,840th Monza built for 1978. Or there about's since the final total is an Odd number. It splits the middle car at 381,296.5 So say, 90,838 to 90,842 were the mid-pack monza's.
My spyder was built 7997 units after the halfway point or about a week later.
I have a trim tag from a car 661 unit's after mid-way. Built on the same day or early the next as the mid-pack cars..