If you’re talking ‘84 SD transmission into ‘85 SE body then all you need is for the speedometer to match whichever differential you’re using (3.07 from SD or 2.47 from SE). The SD transmission should have the same speedometer drive as the SE transmission. It’s a W123 transmission that needs conversion from gear drive to work with a W126 speedometer. Does the SE have traction control?

Sixto
98 E320s sedan and wagon