I know it's not a 6.7 but this is my setup 20x12 with 305/55/20. I did icon 2.5 front springs with fox 2.0 shocks and f350 rear block. Just trying to help as a reference.
Also iirc the 6.7 has more room to accommodate 20x12 with 33's than the 6.0's but I could be wrong.
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