hardened exhaust seats
75k is reasonable milage, but not high by any means, nothing I'd rebuild if everything checked out ok.
I will say, that when I opened up my 302s, the induction hardened head was fine, but the valves were spread and pitted beyond use. I think the induction hardening saved the seats. No idea on mileage. When I put stainless valves in, they checked out square.
Hardened seats are a good idea, especially with higher combustion temps/ 150+ cyl psi applications.
I guess it depends on how much milage you want out of the engine and what kind of heat they will see/ usage. Build it to fit the bill.