Some clues that they are original Camaro bars. The inboard holes match my original stock multi-leaf lower shock mount plates to perfection. The outer holes are aligned just outside of the original multi-leaf hanger brackets, and they have shock mount tabs for staggered shock pattern. I'm also pretty sure Tri five-leaf spring pads are narrower than Camaro also. I've had several sets of these particular bars in the last few years on 3 different Camaro's and one original set on the 70 Nova and all were identical. And the lower angles do not appear to have been added???
If you mount the J bars into the outer holes outside of the hangers and then bring the front into the stirrups, you're bound to see an angle at the front of the J-bar bolts no matter what year they are from. It's impossible not to as it changes the angle when you use the outer holes and pull the fronts in by more than a 1/2".
In you want to assume they are tri-five bars that's ok with me. But I'd say nope. Notta.