[slotard]

14FF axle tubes (that's what my '73 C20 has, so I'll assume you have one too) are 3 3/8" diameter. If you do the axle flip without doing anything else, that leaves 1 1/8" suspension travel (axle to frame distance = leaf to frame - axle diameter) unless you notch it. Add in a softer spring thanks to pulling the overloads and it'll be even less uptravel. You'll need to notch the frame.