I have the original US soundtrack, on vinyl. It includes dialogue from the film as well as a program type book in full color, and maybe a poster or two. I haven't taken it out and looked at or played it in a long while. But I love it and would never part with it - I saw the movie in its original release and bought this album immediately after.
So I would guess that what you heard with the dialogue included was probably this version of the soundtrack.
I have loved this film and soundtrack since I first saw the movie in a theater as a 10 year old kid in 1973. I just recently found another factory sealed copy of the soundtrack on vinyl with no cutouts or holes drilled through the cover. That is a good thing because the 2 posters and 24-page booklet are untouched! One thing I noticed on the IMDB and disagree with is the statement that Isaac Hayes is the uncredited singer of the final song "Tell Me". As far as I know this is not true. It was uncredited yes, but sung by none other than Terry Kath of Chicago who also had the small role in the film. I have seen the original 45 single on vinyl and it does show Vocals: Terry Kath. The actual LP soundtrack does not list his name.