Go wit the w126. The 300se will not have Hydropumatic (not spelled right I know) Only 500's and 560's came with them. By 91 they had everything worked out soild car a little slow but solid. There is not much to say because there were not that many problems with the w126. Not all that complex more of a step behind time by 91. Just check compression, the bottoms of the doors for rust, and that good old tranny. enjoy