There is a 1970 GTO dash on Ebay I looked at. Same as yours, but Ebayer's don't always know what they have and sell it as something it really is not. Pic #1
I also enclosed another 1970 GTO dash restored by Just Dashes and they show the "engine turned aluminum molding" - Pic #3
& another restored GTO car dash Pic #4
Just to throw a wrench in it all, look at Pic #5
, it has both - swirl & flat panel.
answers the question. 1970 Lemans lower dash insert. This is what you have, not the "engine turned aluminum molding" that seems to be on the 1970 GTO/Judges I looked at on the internet.
My restroration guide does not mention the 1970 GTO insert, but it does mention that the 1971-72 GTO had the "engine turned aluminum molding."
Are you sure you have a GTO? Not being funny about it either. Someone could have swapped yours out, or with Pontiac's, very possible yours is indeed factory installed. But I would conclude that the 1970-72 GTO's had the "engine turned aluminum molding" and the Lemans used the plain aluminum molding.