Yeah, on my 1970 Sport Satellite I took the assemblies out and re-installed them . . . the factory must have installed these BEFORE the rear quarter panels went on, would seem the easiest way to do it !!! . . . good luck !!
No, they were installed afterwards...
I have been "told" by some oldtimers, when I was doing Auto Glass, that some Riviera's ( 60's era), you did have to remove the door skin to install the door glass.. Never had to do one, so I cant say for sure..
To the OP. Take your time and have another person help. They can hold it while you snake it back in. Crank the regulator one way or the other while installing to help get it back in and fastened.. If your painted, tape off the edges with some heavier blue masking tape..