I will certainly seek out "The Manitou," especially now as I love your description of the score. Sounds like this and "The Day of the Animals" really need a release at some point.
There was about 15 minutes of music recorded for "The Exorcist" before Schifrin left the film, and they were on a special edition CD that came with VHS and DVD boxsets of the film many years ago. Somebody uploaded the Schifrin music onto YouTube:
