The pan filled C4's are the flared case models, usually only used on larger cars and trucks. Mustang C4's that I have seen were all case filled, step case models. The flared case C4 which is pan filled has a tube which runs down the side, makes a sharp bend to enter the steel pan horizontally, if memory serves me right the tube threads into the pan.The pan is at the very bottom of tranny and covers the tranny filter,valve assembly etc., and the dipstick on a pan filled would enter below the case mounting flange and pan mounting bolts.The case filled tube enters through the aluminum body of the trans itself, from the top just above the tranny to pan mounting flange.