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346s were the first ones (1971) with induction hardened seats.. The 452s were the next evolution. I would put seats into it because the valve job will grind through it.

I find that hard to believe Ethyl additives where in all kinds of fuel sold in 1971, I don't remember excatly when the lead was removed from pump gas but I'm sure it was after 1971 I'm almost sure that the 346 head was a one year only head

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)