Do these heads have hardened seats?

Mopar hardened the iron around the exhaust seat with heat. "Induction hardening". They started around '72, so you really have to know when the heads you have were actually made rather than the production run they had. Also, the induction hardening is not very deep. So if they had a valve job, chances are it went through the factory hardening layer. When in doubt - have new seats installed. But - you might save some pain and simply by EQ Magnum heads with the LA intake pattern. You can buy stock Magnum rockers, and have a much better flowing set of closed chamber heads for less than the cost of the working of a set of original 318 heads.