I know you are seeking answers to why it is a “test” vehicle.
Your Cougar as it sits now has many non-invoice items. Each item needs to be explained.
I am sure I am missing some of the items, but here is my short list, this is what I can recall from memory.
- door and interior panels are from 1970 decore (un-explained)
- high back bucket seats (un-explained)
- eliminator parts (un-explained)
- 351 Cleveland installed (428 replaced by a previous owner)
- Ram air hood missing (previous owner did not want hole in hood without ram air setup)
- many of front end parts/panels have wrong build date (un-explained)
- welds on front fender apron (un-explained)
My suggestion of checking fender apron VIN might explain all above except #4 and #5. I expect you will find a different VIN on fender aprons. My theory is vehicle was in a major front end collision that required those parts to be replaced.
I suspect the owner at the time found an Eliminator as a donor/salvage car (possibly a Boss 302 Eliminator), and transferred Eliminator parts and needed damaged parts to this vehicle.
if fender apron VIN matches was it welded back on replacement panel? Or was damage pulled back out with frame machine and damaged requiring welds? Or are welds there due to typical rust out spots?
As I said before you may need a experienced ford person to do a full inspection like what was done on this vehicle by robert campbell.