Try to buy the dollies that have each caster fastened with a 4 bolt flange vs the dollies that have a single stud. The single stud dollies tend to fold the wheel under when you're rolling it if you snag a rock or a crack in the concrete.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
Got mine from Princess Auto. Heavy duty with steel wheels. Had them for probably close to 20 years with no trouble. Not sure of the quality these days. Those in the picture are for a snowmobile.
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'68 Parisienne 2+2 Convertible Matador Red (Resale Red but not for sale).