You might want to become familiar with Hot Rod Works; http://www.hotrodworks.com/

These guys can set you up with the open drive hardware, the flanged axle setup Jerry referred to, quick changes, they're the go to guys on this. Their open drive conversion is competitively priced with Speedway, but if you're a "buy American" guy the HRW is US made, not Chinese copy like Speedy Bill's.

Not much to add to what the guys have already posted about strength issues, high horsepower and banging shifts will stress it mightily.

As an aside, the best price/value in banjo quick changes right now is the Dick Spadaro kit, though I like the Rodsville unit as it more resembles the Halibrand and is beefier where needed than the old Hals.