My Dad was XO of a Caribou company in SVN in 66-67 IIRC. He was mostly in Can Tho.
The U.S. Army owned and flew those CV-2 Caribous in support of our U.S. Army Special Forces A Camps located along the Cambodian border until the U.S. Air Force took them and renamed them C7-A Caribous sometime around May 1967.
When the Army flew CV-2s, they were usually piloted by Warrant Officers with SP5 Crew Chiefs and wouldn't hesitate to land on our dirt runways, but when the Air Force took them, they were usually piloted by Lieutenant Colonels or Majors with Master Sergeant Crew Chiefs and would only land their C7As on paved runways.
Please pass my thanks to your Dad. Those CV-2 Caribous were used for everything from resupply to medevac and were one of our greatest assets.