The 300CE would be able to take a manual transmission, which one depends what year and engine you have (m103 vs m104). Not sure about the 500E, maybe a later model manual from a 500SL would line up? Not sure

__________________
TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth