Okay...I'll "pipe in" here...
In my research, the HCS was a separate deal made in the late spring to send some of the GT/CS cars to Colorado, more specifically, the Denver district, DSO 51. If you look closely at your HCS invoice, you'll see a "71" number buried within another number at the right bottom of the window sticker. This meant that the L.A. district made a deal to send cars.
What that means in "Ford-Dealer-ese" is that the HCS cars ARE GT/CS cars sent to Denver WITHOUT script, and NO stripes on the scoop. Easy to do at the factory (although they complained). That may be why Marti's report says "GT/CS", when it's a HCS. The HCS was kind of a last minute deal to get some cars out for sale, since the GT/CS really didn't take off immediately. So...since Colo. dealers did the HCS for '66 and '67, they had some marketing clout. It's easier to call it that on Ford paperwork, then to get into explaining what happened with the Colo. Ford Dealer's Assn., etc..
SOoo.....We need to get someone to nail down from Marti EXACTLY what the number is. Is it 4118, 4117? and are the 251 '68 HCS cars INCLUDED in that GT/CS total number or not? We need to know exactly how many of the (Ford named) "GT/CS" (actually HCS) cars have a DSO 51 designation. If the number is lower--that could affect values.
I hope this helps....
Paul.