>I see no evidence for or reason to think Eliot ever took any 
>spiritualism of that kind seriously.  If you have any text that 
>does, I would like to see.

I agree that Eliot never took that seriously -- was in fact dismissive of it -- but in thinking about the matter I realize that what intrigues me is not whether Eliot believed the living could talk to the dead -- anyone can talk to anything -- but whether he believed that the dead might be trying to talk to the living. I know that sounds exactly like the sort of naive hocus-pocus he was scornful of, but at least on one level it clearly isn't: dead writers whose works we still keep reading are talking to us, the living. But beyond that metaphorical level of "talking," Eliot sometimes seems to believe, or seems to want to believe, that the dead are trying to communicate with the living. In "Little Gidding" he says that 

          what the dead had no speech for, when living, 
     They can tell you, being dead: the communication
     Of the dead is tongued with fire beyond the language of the living.

That's Dantesque, but it's Eliot, not Dante. And later in "Little Gidding" there's this anecdote: "I caught the sudden look of some dead master," followed several lines later by the dead master saying, among other things, "I find words I never thought to speak / In streets I never thought I should revisit / When I left my body on a distant shore." Whether the anecdote is an account of a mystic vision or completely fictional, it respectfully, not scornfully, imagines the dead speaking to the living. The anecdote is the product of the same imagination that in "Ash-Wednesday" has the bones of the dead speak and sing. And before Eliot's conversion, there was Prufrock, imagining what he might have said as Lazarus, "come from the dead, / Come back to tell you all." 

I've used the word "imagines" or "imagination" a lot because I don't find any reason to think that Eliot actually heard voices of the dead. It does seem to me, however, that he wanted to. Whether he thought it was possible to, I don't know. Maybe he thought it might be under certain conditions (at the still point of the turning world, etc.).