But you also need some force from the bolt to push on the hub of the pulley. The key could never hold that much force by itself, if the crankshaft is slightly longer than the pulley hub (because the tolerances are not checked and matched at assy.) no matter how tight you go on the crank bolt the key will break.

I would install the pulley but only tourqe the bolt a little, remove the bolt and see if you need to shim behind the pulley hub.

My $.02.