I HAVE TWO OLDER 6X4 GATORS THAT BOTH NEED REBUILT AND I WAS WONDERING IF ANYONE HAS REMOVED THE ORIGINAL FD620 AND REPLACED IT WITH THE FH601. I THINK BUT NOT FOR SHORE IN 2005 JOHN DEERE CHANGED MOTORS AND PUT THE FH601 AIR COOLED ENGINE IN THE 6X4. PRIOR TO 2005 IT WAS THE FD620 WATER COOLED...