C-20 front wheel rubbing

[steves1967]

I added 20" Detroit steel wheels to my 71 c-20. I have as much offset as DS can build into the wheels but the front wheels still rub the inside lip of the fender when the suspension compresses. Ive looked at other trucks that seem to have no problem tucking the wheel into the wheel well. Could this be a wheel issue, and disk brake issue, or maybe it's the 2" dropped spindle issue? I know on other cars adding disk brakes pushes the wheel out a bit... any ideas? Id like to lower the front some more.