[Jack21]

MSD ships its distributors with cast iron cam gear and is intended for use with cast iron hydraulic (or solid) lifter camshafts. The dist usually (mine did) has a tag on it warning the end user to change the distributor gear to a steel gear if the engine has a roller cam which is made out of steel, not cast iron.

If you have a roller cam specially made with a cast iron cam gear, than use a cast iron distributor gear. Don't know of any Ford roller camshafts that can be made with cast iron gear.