1f you have to replace 75% of the sheet metal, 100% of the running gear and interior, 90% of the glass and 100% of the trim, what do you really have?
I guess that's why I kept the VIN and Cowl tag from the one I sent it away.
You'd have a rebuilt car.
If a '69 got popped in a different corner or side every 2 months for two years since new, and repaired correctly each time, you'd have the same thing. Doubtful anyone would junk the car in 2014 if it was discovered many panels were no longer original. As long as the seller discloses the rebuild information I see no issue with it. A car with all original tin can be found if a person prefers.