WOL mounted his ARB fridge on top of the Tuffy deck, I recall reading the 50qt size fitted but 63qt was too tall. Which size ARB do you have ?
My Engel fridge fits well on top of the Bestop trunk rack (installed before Tuffy released their deck). Also a number of JKs with fridges are in this thread : 'Expedition Modded Jeeps - Let's see 'em!!'.