I might as well bring this up here.......
I bought and old 181 pulley, haven't installed it yet BUT, the instructions call for heating the center hub to over 200 degrees F in an oven then sliding it on the cold crankshaft. To me this would indicate a press fit. I have not heard of anybody else even mentioning this step. I can't see how a piece of keystock could hold 8 pounds of pulley inertia.