Sorry, I'll clarify...some C4's had a dipstick tube which entered the trans through the case near the passenger side front of the main trans case....others had a dipstick which entered the trans through a bung on the pan...
Usually, the trans with the pan mounted dipstick tubes had the larger bellhousing and were generally a later model trans...
If you go to most trans sites, like TCI, you'll see some descriptions of the features which determine the different years...in general, of course...
I've only worked on early stuff so I'm going by what I read on this subject...maybe someone else will have better info...
Pat
http://www.jps.net/binay/webdocs/strtmstng002_sml.JPG