Thank you. I have to learn that now I am required to verify my facts since the accident last year. Correct, not sodium filled it's Stellite faced (coated) exhaust valves. Those valves were supposedly only the -3 engines.
No worries. I only know from deep diving into sodium valves for an RV motor build.
You are correct that they are premium valves for severe duty.
Do you happen to know if the heads have seat inserts?