Great question! I had 3 choices. All three would have worked.
3). New was about 55 bucks at my door. I had pretty much bought all the components for the build, and there was room for them in the budget.
My thought process was the exhaust valves were 40 years old and had 120,000 miles on them. The exhaust valves take a beaten. Means the funds allowed it, why not new?