I've found the windows - especially quarter glass - to be a PITA.
Another is the '68-'69 dash switch panel & troubleshooting/replacing those switches.

Been through the re-work hassles, too.

If it was all easy, I'd be fine with that; but the satisfaction of getting things corrected might not be as good.
What's intriguing to me is how some cars are easy, and some fight all the way through.