It sort of depends on where the cam makes power. With an OEM stock cam, you can run any gear ratio that you want to, 2.29/2.56/2.73/3.07. With an aftermarket cam of the "RV" type, you will want to use a little more gear, maybe a 3.31/3.55 or 3.73. With a lumpy cam, you might want to use a 4.11 at a minimum and more than likely a 4.56/4.88. These are just general guesstimates to give you an idea to start from.