I did my boss302 with both glass in place, not sure if it's the same on the 67.
As I recall there were "grabbers" almost like carpet tack strip near both windows. It's a tricky job.
After doing it once myself, I'll tell you this, if the upholstry shop will do it for a reasonable fee, have them do it. It's one of those things that takes experienced feel to get just right.
Good luck with it!