I used an SBC, short water pump, single groove crank pulley like for a '65, 327, o'rielly's had it in chrome on the shelf, 20 bux
The balancer bolt has to go in first, then the pulley 3 bolt pattern, its the same pattern for BBC and SBC
Jegs and summit both have aluminum ones for cheap, too. I used an aluminum on my 454, dont remember if it was SBC or BBC
that was 5 years ago...
Dan'l