67 C-20 wheels

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I am restoring a 1967 c-20 chassis cab that has a steel bed. The truck ahs the original brake drums that are in good condition, the problem is the truck has original rims that overlap each other (like spilt rims but without the round bar that holds the rim together). My question is what year truck rim do i need to look for to replace this type rim. I have tried a later model dually rim but this rim will not clear the drum. This c-20 truck has dual rear tires. Any help would be apreciated