OK--I'm confused, Auto Trans adjust.

[MS Fowler]

I searched the forums and my Haynes manual, and I'm still confused....
My car is a 1982 240D ( 123.123) The automatic trans shifts a bit early, going into 4th at 50mph whereas, according to the markings on the speedo, it should stay in third up to 60. Other shifts are similarly early; at least as compared to the speedo markings.
First...are the markings on the speedo where it should shift at WOT?
Second, if I can raise the shift points, How do I do it? The Haynes manula has very clear instructions for adjusting the linkage that from the throttle to the transmission. My problem is that I can't find any such linkage. Were some of these made with vacuum information ONLY?--or has some PO removed the linkage (doubtful)?
Michael