Since no timing marks are involved on a stovebolt balancer, the placement of the keyway isn't critical. If the keyway in the balancer is damaged, either have a new one broached in a different position, or just replace the balancer with a good one. Getting the keyway in the crankshaft straightened up and making a key fit tight is the critical operation.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!