Some gasket kits come with a thin paper-like adhesive gasket in them that you can use... but NEVER use cork. as they always harden up and blow out causing leaks.IMO whether you use a thin gasket or not, it should still have a silicone bead around it to be safe.Prior to reinstallation of the sump, ensure the sump flange is flat. Turn it upside down on a flat level surface and go around it with a mallet in case its bent.Then clean both surfaces with metho before reinstallation with a quality hi-temp gasket sealer.I found that some brands like Permatex dry quite hard and not very flexible when dry thus ends up blowing out and leaking oil.I wont use anything other than 3Bond No.1 Grey RTV Silicone Super Sealer anymore. I use it on sumps and gearbox casings and it stretches out like a baloon when dry = great flexibility!!
Not many places stock it but when I need it I buy from http://www.fullnoise.net.au and it gets to me either the next working day or the day after B)