This is the sixty four million dollar question to which there is no absolute right answer. The shelves are full of gaskets in tubes and the choice seems endless. In the old days I used to go with Blue Hylomar and a paper gasket. That's what I would have used the last time I sumped a V8 engine. Nowadays sump gaskets seem more sophisticated, being either an O ring in a groove or a metal/rubber composite. Even so, on the Ford V6 it's recommended that you use a sealer at least where the front cover attaches to the block.
So all I can say is do a bit of research - go for one which stays flexible, is oil and temperature tolerant and bear in mind that one day you might want to take it off again!
