Normally (always exceptions) Ford company cars were moved in one of two ways: (1) the "B" plan resale lot that moved around to a few locations in the 70's and 80's in Dearborn, (2) destroyed.
We have procured "B" plan cars that were executive leases turned in after the year lease was up, and also "pool" cars held by various departments. The employee lease cars were generally not tampered with since it would come back on the employee if there was an issue, not to mention it was primary transportation so why take the risk. The pool cars were not supposed to be modified, or were to be returned to normal (test equipment and parts removed) before sale. I picked up a four year old Escort one time that had 4k miles.
That said, if there were lease cars outside of the SE Michigan area (executives at assembly plants, Philco-Ford locations, etc.) I'm not sure how those were transitioned out. Perhaps through local dealers.
Cars that were significantly tampered with for testing purposes were (should have been) destroyed, and then recycled. In the 80's Ford was using Environ out of Romulus to recycle parts. There are also a lot of good rumors about the cars that were supposed to have been destroyed that disappeared.
I've never heard of the Ford Marketing National Resale System. Will keep my eyes and ears peeled. John