I can only be 100% sure of this installation procedure being correct at the Belvidere Plant. I think I saw it at St Louis. (memory fades with time)

Wiper assembly was done on trim line 1.

Operator climbed into car with 2 air hose guns and stood up thru the empty windshield opening. One of his coworkers then handed him the wiper transmission. He fished it in and took bolts which he carried in his apron and fastened the linkage.
Then he exited the car, and handed a assembly to the next guy who was already in the next car and so on and so on for eight or 9 hours. Up down, up down.

As I remember when we ran 65 cars a hour there were 3 men assigned to this job. So the worker had approximately 3 minutes to do his job
When the line speed was cut they cut personnel accordingly.

This sounds strange, but it is really easy to put them in this way. No Dash pad, no windshield, just a empty body.

Try it, it works.