6620 with 4 row head

My father and I were looking for a different combine for our small family farm last winter and found a really nice 1988 John Deere 6620 Titan II with 2200 Hours. We had a 4420 with a 4 row 38" head. Now we got the 6620 home and found out it will drive on the two outside rows with our current 4 row set up. The dealership took out the spacers for 6 rows on 30" to move the tires in. Has anyone ever had this set up and have any ideas on how to get the tires off the row. Thanks