Dual wheel size?

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I just recently acquired my grandfathers old wood hauling/beekeeping truck that he heavily beefed up in the past. Anyways I was wondering what size Dual wheels will fit on these trucks it is a 1978 K20 with a 14 bolt rear my grandfather said he always ran 16" wheels even with the duals but not sur eif he remebers correctly cause he is 82 years old. So just wondering if 16" duals would fit on the 14bolt rear cause the the drums are so large.