Why is Morticia overdubbed in this episode of The Addams Family, and what does she originally say?

Not an actual answer, but my speculation is too long for a comment.

The voice is an excellent match, but I wouldn't rule out the possibility that it's just a good imitation and the replacement is recent. From the video quality and the fact that there's no logo in the corner, I guess that this must be a recent re-release, not just a home recording of the same version of the episode that's been in reruns forever.

We usually think of censorship as running the other direction, but sometimes when an old show is repackaged the new distributors decide that what was acceptable in the original broadcast isn't acceptable now.

For example, jokes involving racial stereotypes might be removed to save us from being uncomfortable, or something that used to be just a normal phrase is now a well-known slang term with a meaning that's "not appropriate for all viewers". I don't think either of those applies here.

There's another kind of censorship that's done not to "protect" the audience but to protect the distributors: removal of names. If a person is named in a sitcom joke and threatens or files a lawsuit about it, they might censor the name in reruns. That's probably not the case here either.

The possibility that I think is most likely is that a name that was removed, but rather than the name of a person it's the name of a company or product. Furthermore, I guess that "[something] kind of tastes, [something] kind of interests" is a reference to an advertising slogan, and the addition of "[something] kind of head" worked as a joke because the [something] had some resemblance or relationship to a bald head.

The conclusion to my guess is that when the episode was being repackaged for release on DVD or Netflix or wherever you got it, it got passed by a fresh batch of lawyers, and one of them decided that without the permission of the [something] company (which still exists, although the referenced product may not), it was not acceptable to use the name. (Also the joke no longer works because the audience has forgotten the reference anyway so not much was lost by removing it.)