Peter,
I ground that lug on the calipers because when I first installed them they were hitting the brackets. Your right, there was no way the bolts were going to line up in the brackets without doing so. I also had to grind the casting around where the brake hose end fits onto the caliper. The casting was setup for a hose that had rounded ends on it whereas my hoses had squared ends, so I had to relieve this area slightly. I checked to make sure that I had adequate clearance and that I didn't have any interference between the caliper and bracket after grinding and I was good to go. The bolts went in easily when I all I had was the empty caliper sliding over the rotor and bolting it up that way. I really had to work with the bolts to get them started after putting the pads in the calipers. I noticed the brake pads were thicker than most I've seen for some reason.(I've seen a bunch of them, used to work in engineering for a facility that made them a few years ago
) I wonder if this could be the cause of it?