Thanks very much, Paige. And my apologies for the delay in responding; I didn't get notification you'd replied.
I've since found information that Joan HORN m. Joseph Theodore LINZMAIER. He was b. 1933/4 in Wisconsin. I've contacted family tree owners who note this marriage but have yet to get a reply.
I don't know which person was Joan's last husband, although I suspect it was KLICKO. Even if she hadn't changed her name with Social Security, the Florida death record (I've now located it and will be ordering) would surely reflect her current surname at date of death, as given by the informant.