FlexHone and file fit plasma moly rings are an option. yes it is a ridge & needs to be removed (rent a ridge reamer & carefull use of it, more on that if/when you get ready to use it) for new rings to be installed on a rering (no rebore). You could take one of your old compression rings & square up the ends & use it to measure taper and out of round amt to a fair degree. iirc way back a Mopar mag mentioned that 346 heads may or may not be induction hardened (someone will clarify) as it was a transition period.