I love the series, too. The best -- and least respected -- ensemble on network TV.
The music they do fudge a bit, which I entirely forgive. I was the exact age of Meg at that time, and they tend to choose songs in a 3-4 year window, not holding to the actualy top 40 of any month in 65 or 66. It was a rich era for music, with many influences peaking: Motown and pop synthesized, too. (DREAMGIRLS fans -- this is the era that show nails.) They are using more now, but before have used less of the "British Invasion" music, since it may be harder to approximate with American guests. But it was heyday of good ol American rock. Remember, the pop angle was very mainstream -- we had Petula Clark consistently in the top 10. Unless I've missed something curiously missing from the show is a hot couple of that moment: Sonny and Cher. They had number one hits.
"I'm a comedian, but in my spare time, things bother me." Garry Shandling