S-class problems

Fantastic site . I am intrested in getting an s-class sedan . I am looking at a W126 560SEL from 1990 with 140k , highway miles mostly . Beautiful car , what are some pros-cons , things to be werey of ? Second I have always loved the W140 , a V-8 especialy . I was wondering if you could shed light on the"steering shimmy in the earlier cars . How long was it present ,was it all the models , hoew severe , is there a fix , ect. ?. Would a 500SEL (From 92 or 93 ) be a better choice ? thanks alot .