The first time I flew on a 707 was on a Wardair affinity* charter from Calgary to Gatwick in the early 70s. They had two - a
707-311C and 707-396C.
Here's CF-ZYP at Gatwick with a CP Air DC-8 behind:
Who does the other DC-8 belong to?
* Before the rules were simplified, passengers had to be members of an association that chartered the aircraft. I was a member of the Calgary Firefighters Association!