Patto,
According to the Mustang Recognition guide, the '67 shared the glass from '66 and was NOT the same as the '68, which had different curves on it. Maybe your original channels are right. I hope this helps your dilimma, otherwise a call to Phil Whickham in Newcastle (02)49908677 may help as I know he has a limited stock of second hand channels and glass.
Cheers, Ron B