Hi Jason i have fitted nissan 4spot calipers to drb's and workes great even on hq rotors but there is a lot of clearance problem s we had to notch the lower control arm and the cut the bump of the cross member at the back.
anoter option is the small 4spot willwood calipers ap calipers with radial mounts as they fit pretty easy.
also i would recomend going to s/s braided lines gives a great pedal.
regards oz
