according to the spec sheet with the rings
top ring
bore size in inches x 0.004 + 0.004 (for turbo app)
bottom
bore size in inches x 0.005 + 0.004 (for turbo app)
now, after some research and consultation with a race engine builder and Ross themselves we gapped to 0.014 top, 0.016 bottom on 2.933 (74.5mm) bore size, which is roughtly 2 thou below spec.