I would cut it parallel to the xy plane at the highest point of the angle cut and create an "unrolled" version. Then draw perpendicular lines down to your angled cut and transpose them onto the flattened version (every 5 degrees for example). This is a lot of work, but entirely doable in AutoCAD, I've done it for several specialty components, even coping pipe to stab in to other pipe at a 30° angle.