A lot of guys swear that you need one of those steel core neoprene deals or the MP "O-ring" style gasket.... and I am sure that they both will work well. However, you don't need to spend the money. A factory style CORK gasket will work just fine. Make sure that the pan is not deformed and that both mating surfaces are clean. Also, torque the pan bolts to the proper spec, (15 ft-lbs, I think). It has been recommended to me to stay away from aftermarket stamped chrome pans. They are too thin and will deform when you tighten the bolts and the chrome surface does not seal well. Use either a straight original pan or a cast aluminum pan.
BUT FIRST, make sure that it is in fact the pan that is leaking. A local transmission guy recommended that I clean the entire bottom of the transmission with brake or carb cleaner. Then, get some Dr. Scholl's Spray On Foot Powder. Spray the stuff around the pan gasket area, dip stick tube, shifter stud, coolant lines, etc. Let the car run long enough to get up to operating temperature, shut it off, then climb under the car and look for the red fluid. It will be easy to see against the white foot powder.
I lost some of the few remaining hairs that I had left trying to get a pan gasket to seal when it ended up being an O-ring on the rear of the transmission just above the pan where a pilot shaft exits the housing. The fluid would leak past the O-ring, run along the top of the pan toward the front of the car and drip right under where the dip stick tube goes.
