If your stock unit is in good shape go ahead and use it. If not then get a nicer aftermarket piece, keep in mind that many aftermarket dampers wont allow the stock pulleys to work. Check carefully before buying. My bet would be to get a stock replacement if yours is shot. You dont need a high dollar damper in my opinion for a 400 hp motor, my 360 is living just fine with the stocker and its a 400hp motor.