235/85/16 LT E rated tires are the standard size for a '99-'04 Ford Superduty F250 or F350. They are way oversize for a '54 3100 and require a wheel that's 7 inches wide. The standard wheels for a 3100 are 4 or 4.5 inches wide.
I believe that some of the guys here have recommended 215/85R16. C load rated tires would be plenty for what you need. Higher load rated tires would give you a much stiffer ride, bordering on tooth-rattling.
