That is a lovely group of choppers and I did notice a bit of variety in the collection but if you are going for the Apocalypse Now Ride of the Valkyries scene you need even more variety because there was a rather eclectic collection of choppers used in that sequence - not close to all were hueys. Though I'm betting that was more about budget and availability for the film maker than what the reality might have been in The Nam.
Served in '76 with sailor who was involved in the evacuation of Saigon on board the same ship we were on - quite a tale he told, and turned as white as the background on my screen as he told it. Chopper after chopper tried landing on the helicopter deck on the fantail (it was a missile frigate) and sometimes one landed right on top of another and all the crew could do was push both into the sea because another chopper was coming in to land - all of them running out of fuel, some ditching in the ocean. Plus they were on fire and fire is the mortal enemy of a ship, even a ship made out of metal. In the last year or two saw part of a documentary talking about this finally. For decades my only source of knowledge was the first hand account. Pretty horrific.