The W140 AMG was available also in part "ala-carte". The complete take over of AMG was around 1993/1994... but I've seen the W140 get parts purchased in accesory form, not a factory AMG-Mercedes form. I've seen rear tables as well for the W140.. something the factory did not do. There are plenty of these W140 AMG's available in Japan. They shared the same AMG engines that were available on the 500SL AMG's at the time. The 500E (same time period) also were available tuned by the semi-private AMG company at the time.

Below is a company picture of a W140 AMG: