Just a different point of view.The crank on my two 261's and one 235 were drilled when the crank was at the machinist.Can't use a retainer bolt as the shortened water pump leaves the fan passing a scant 1/4 inch from the damper.So the threaded hole would accept a tool to draw the pulley on.Well, not me the hack, all three dampers were installed with a 5 pound mash hammer and large drift , 4 blows and you're good to go.Some say the hammering ruins the thrust bearing. Those cranks weigh in the neighborhood of 80 pounds, a lot of metal to absorb the impact.My 261 powered 37 is run pretty hard, pulling a travel trailer long distances at 3000 rpm .The damper hasn't flown off yet,.Many of those old dampers are a sloppy fit on the crank , everytime it gets pulled off, a little metal comes with it.So a bolt is good insurance if you have any doubts. Sixpack drives like a maniac,dampers fly off and he runs them Jimmys till they explode.
