14" Ralley wheel fit issues

A lot of people don't realize you are supposed to measure them at the bead, not the outside of the flange. So it's often ambiguous what the actual size is. That said, 4" backspace is definitely not an OEM rim. They should be around 3.5–3.75, IIRC. My OEM rally wheels fit fine with the OEM K-H calipers.

Personally, I would not run a spacer. But that would be better than grinding down the caliper, which sounds dicey. How much are we talking about grinding? They are hefty for a reason.