Some interesting trivia-
the Lear 8-track is from the Lear Jet company- Mr. Lear was instrumental in advancing the 8-track technology in those days, and was one of the first to go into production. Obviously he had better luck with the jets. There is no connection to Pontiac- it was strictly aftermarket.
1967 was the first year that GM ever offered taped music in ANY car. FM radio was also very new, with only a few stations in the country at that time.
So, these "premium" audio systems were very swank and very cutting edge technology for the times.
The 67-8 units were huge boxes, and every GM car used the same core unit, they just changed the trim and mountings. 69-70 was a much more compact underdash design, and by the mid 70s, they had the in-dash units, but cassettes were already killing 8-track by then.
Right now, there is a small niche of people who restore the audio in their cars, but most are turned away by the cost, especially when they know they'll have a crappy sound when its done.
IMHO, tho, given the history, these audio restorations will gain in popularity and will enhance the value of restored cars.
BTW, there are many internet sites dedicated to 8-tracks, and you can get a wide variety of used or even new-in-box 8-track tapes from the era. If you look hard enough, you can even find the original GM demo tape that came with the car, as I did.
Good luck and have fun!