How about putting some RTC on the filler tube above the O ring' Ley it sit for an hour and then install it. Letting it sit before installing it has been the trick for me to get it to seal.

A deep pan gives so many extra benefits. I have a aluminum deep pan with a single tube Moroso cooler. Nothing goes through the radiator. Driving on the raod the oil never goes above 200 and when I raced at the drag strip it never goes above 200. They say that it should "ideally" run around 180. 200 dergress will make you need to change trans fluid every 50,000 instesd of 60,000. Of course if you tow, you will need a bigger trans cooler. Next week sermon "Deep oil pan VS speed bumps".