I don't mean to sound like the "search Nazi" because we're always open to questions here in the convertible forum, but....
You should really familiarize yourself with NICO's search functions.
There are quite a few threads and discussions about changing oil pan gasket and dropping sub-frames, etc...
The best info you can get is in the Full Service Manual. We have that hosted for you on NICOclub.
Here is the link to directory of files.
http://www.nicoclub.com/FSM/240sx/91-94/
I think the EM is the engine one if I remember correctly.