Putting a JD843 corn head on an R72 Gleaner.  Does the sprocket ratio on the John Deere corn head need to be changed?  Currently, I have reversed the sprockets that drive the corn head but it still seems like it runs awful fast.  Do I need to slow it down more?  Do I need to run the feeder speed on the combine on the slow or fast speed for corn?  Do I leave the drum height blocks in the grain position for both corn and beans?