Also I just remembered Your Balancer will have one 3/16 keyway The blower hub will have two 1/4" Keyway's
The crank needs to be milled for the two 1/4 keyways. You can buy a 1/4-3/16 step key stock. I wouldn't recommend it
Especially if you race it or run a high boost, I will snap the key off.
You might get away with it running low boost with a small 671 blower, with red loctite and tighten the shit out of a ARP crank bolt.
The first time the blower backfires It will probably snap the key off.