I have a 66 coupe, and the wipers work great, except they go too far over at the up position, and not all the way down when returning to home base (while running, that is,,,, they return to proper position when actually turned off).

need some advise please on adjusting them (hope I can do it!)

 

I had the exact same problem. Not an easy fix, unfortunately. I had to remove the wiper motor and I took it to an generator/starter repair shop and they repaired the gearbox that sits on the wiper motor.