Hey 270 I think you could grind them down enough with no problem and I don't think it would be nessacary to have it completely smooth. You can remove some material pretty fast with a grinder and the right wheel.Get a fast cutting wheel and angle so as to use the tip of the blade and that will remove material faster and once you get close level your grinder out to smooth your ridges out some. I think you'll be fine w/ a 4'' grinder and a little patience. Good Luck