Many times I have pulled old siding off of homes and found moisture trapped between the tar paper and the inside boards or plywood. This caused rotting and mildew with the resulting odors.
I personnaly would never put tarpaper under any type of siding.
I am also of the opinion that the tyvek type products are overrated. I don't believe it was available in 1975.
I think what you have is common practice for the time.