Look up "Fast Monty's Garage" on YouTube. He has a 69 GTO. He just recently did a video about AN radiator fittings.
It's not so much my thing, even tho I LOVE the functionality of AN fittings for fuel lines, and I HATE twisting off stuck hoses and clamps.
https://youtu.be/ywt1HtPKtJ4?si=En8bs1gfFYdZsXqi
He also did a number of videos about fan cfm comparisons. Because of his videos, I bought a brushless fan for the slow startup current instead of the huge starting spike for a conventional fan