Use new gasket, use Ultra Copper. Ultra Grey is useless on this - I have it on mine and it still leaks lil bit. Don't use lockwashers - it will leak, just use the Copper Washers.

Also I am doing this with a next oil change:

"Permatex #2, non-hardening, on the drain flange bolts. Those effers go all the way through, and threads don't seal all the way around- there's always a gap at the "points" of the threads on both the bolt and the nut, and oil's designed to capilary through just that kind of path. Add in the pressure of blow-by, and (as you've found) it'll drive you nuts."