James,
I do lots of grading with my 322 with a 54 front blade. More rear weight is always helpful (200-300 out back)as are chains if you are running turfs. Make sure your cutting edge isn't worn down to the main blade. I quit using JD cutting blades.The one on my 54 blade now is 3"x1/2" 54" hot rolled that I ran a weld bead of hard surface on the bottom edge. It takes 5 to 6 sticks at a buck a stick (money well spent). You will find that you will get best results grading in a reverse direction. If you have a 3 point hitch, a 60" landscape rake works good for spreading and smoothing gravel in the forward direction. Dirtworks makes one that isn't too expensive and works pretty good. If you abuse it the tines will bend,but you can bend them back.
A center blade would be great,but they don't grow on trees. Who knows maybe if you asked in the wanted section...