I've had issues with stuff from Classic Parts, too, as well as other places. In general, reproduction parts are a crap shoot. In this case though, I do think their vent window seals are good.
http://67-72chevytrucks.com/vboard/s...d.php?t=660294
https://67-72chevytrucks.com/vboard/...d.php?t=820567
I am happy with the Precision window opening lip seal/felt set I put on my truck. The outer one with the chrome strip doesn't look or fit the same way factory units did, but it is good quality.