I have those books. Somewhere, buried in my library of fitness books and mags :-)
Seems to me those exercises are still perfectly valid. I still use variations of them today - just had forgotten the source.
Since using those books, I've supplemented with swiss-ball crunches and other exercises. The swiss-ball works well for me, but hard to generalize to all bodies.
You've inspired me to go back and try and find my books and give them a whirl.