I recently found a 69 convertible with a custom 6 tail light rear clip. It appears to be part of a modification done by a custom painter named "Kolors by Billy". The clip uses the stock quarter bumpers and the mini flare behind the rear tire like the 70's clip.
It also uses the stock tail lights and tapers the rear spoiler to a thin edge. I have started a body off restoration since it does have matching vin engine and correct code trans and rear-end.
Has anyone seen this done? Would I be better off rebuilding to stock?

It's your car and your money, but since everything is numbers matching, and you're already beginning a body off, I would keep everything stock. That would help preserve its future value. If it wasn't numbers matching, then do whatever you like, since it would never have the value it might otherwise. Custom Vettes, no matter how well done, don't seem to maintain their value to anyone other than the person who had the customizing done.

Thanks for the info, I have located a factory correct rear clip and plan on returning the car to stock. I also plan on improving the suspension with performance springs and shocks. This is a show/driver restoration that I want to be as fun to drive as to look at. Will these suspension upgrades hurt the value?