The only difference AFAIK is the mounting boss for the crank position sensor. It's on the top of the bellhousing on the exhaust side.
http://zhome.com/ZCMnL/tech/240SX5spd/571C_left.jpg
You can see it right below the (OK) on this trans.
AFAIK all S14s have this. On my late late '93 S13 there's a raised surface there in the casting but no drilled holes. On most S13 transmissions there's nothing there. You should actually be able to just use your crank position sensor (or its mounting boss on your auto trans) as a template and drill the holes in an S13 trans.