Hardened Valve Seats or Not?

I put hardened seat in my 67 slant 6 because even using lead replacement additive I still had seat erosion. way back when, it was not that expensive, and it was exhaust valves only.

If you do it now you won't have to worry. I don't remember when lead free gas came into to usage. but I think if heads were made prior to lead free gas it would be prudent and one more thing to not worry about.

Omar