I can't help on the experience part but 600 x 20 would be 32" x 6". I sure wouldn't want to downsize the rear tires by 2" as the trucks are geared low enough already!
I'm not sure my point was clear. Those are two distinctly DIFFERENT tire sizes listed! I found it at Universal. It looks to be very narrow but large enough on the O.D. Hopefully someone that has them can chime in.
600-20 US Royal Blackwall
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600-20 US Royal Blackwall
Perfect for truck applications! Made in the USA Details/Options
SKU U75580 Construction Tube Type 6 ply Polyester Load Capacity 1,350 lbs. @ 36 psi Overall Diameter 32.20" Tread Width 4.20" Suggested Rim Width 3-4"