Over the last several weeks i have reinstalled the side and roll-up quarter windows on my 69 Coronet. It's not a post but they should be very similar. If it's any consolation I found the quarter windows to be trickier than the sides. More experienced members may disagree, but I highly recommend having someone help you. One person slides the assembly down while the other guides.
If not already installed, hook up the locking mechanisms, door handles, etc. it's much easier with the glass out and they don't interfere. Bolt up the front bracket that the vent frame fork aligns with, and the rear channel guide; bolts can be hand tight. Install the window regulator with crank handle. Double tape both sides of the door frame opening because no matter how careful you are, the assembly will hit and chip the paint. Remember to remove the tape before locking the assembly down otherwise it will be wedged between the vent frame and door (don't want to say how I know that). If you're replacing the cat's whiskers, install them last, gives you more room.
The side window and vent frame are installed as one unit. The vent frame should have the lower channel frame attached along with the adjusting stud (don't know exactly what you call it) at the bottom. BTW, there should be anti-rattle foam between the stud and the two-ring holder. Most of the time it has disintegrated over the years; I just used foam rubber insulation cut into strips.
While one person drops the assembly down through the door from the exterior side, the other person guides it from the interior side. The trickiest part is aligning the regulator arm with the bottom window bracket. Once it's in the assembly should slide right down. For me, the passenger side took maybe 5 minutes to install. The driver's side front fork wouldn't align with the bracket so I had to drop the window down first and then install the bracket. It was a pain but it finally went.
The most time consuming part is the alignment, especially if you installed all new weatherstripping. The FSM is a good starting reference, but in the end it's back to two people, one cranking on the adjusters and the other person eyeballing the movement. Take your time and you'll be OK.
