leaking aluminum intake gaskets

I have 2 cars that I cant seem to seal the intake from leaking oil. first car is my 70 duster with a 360 in it. It has a edelbrock torker on it. The other is my 72 scamp. it has a 408 stroker with an offenhouser dual 4 BBL intake. I am not using the cork end seals. Im just using RTV on both ends. Any suggestions?