If your pan uses the stiffening rails, the one piece gasket is the correct one.
If your pan DOESN'T (a stock front sump 289 pan, for example) you need the 4 piece setup.
If you have an aftermarket pan, call the folks who made it and ask them.
Just bought oneI used the Ford Racing 1 piece gasket and it works great. $18 at summit as opposed to the $40 felpro 1 piece.