You could always just totally transform the standard "Haunting" incl in the book to be a different kind of haunted house, make the hooking of the players really interesting, they could find the house, it could be a drunken roman dare, maybe they need to put down suspected rebel activity, runaway slave/wife/child, subversive religious group, w/e
And it would be easy to stash clues to further mystery in the house or the ruin (in the 1920s setting its an old church i think). Put random crap in the basement(ghouls, a horror from beyond, a mythos tome) have it open into the catacombs, freaky frescoes, a ghost.
I dunno, you're just making me want to run that game.
Good luck, its a lot of fun!