Pitman/Tie rod taper

Does anyone know the taper of c-body pitman arm stud as compared to other common angles (7 an 10 degrees). And I know it's "larger" than a-body stuff, but I'm looking for actual numbers. I'm getting a measurement of ~18 degrees on my '71 pitman arm stud so I'm getting confused as well. I need to ream out the pitman/idler holes in my center link to accept full-size pieces and get fast ratio steering. Thanks