From all the forums I've seen (Offshore Only and others), the Blackhawks were like pre-XR Bravos. Could handle HP up to about 550HP but then it was a 75 to 100 hour rebuild cycle. Very durable at 350HP. I've also heard that they can be rebuilt with XR parts for better durability but not more power.
Remember these drives came out in the 1990's when big power was rare and were not designed for more than a stock 502.