Alpha's can handle higher HP levels behind a SBC much easier than a BBC. The extra torque the BBC makes will break the Alpha much easier. If you drive the boat with sense and do not hammer the holeshot you should be fine. Keep the prop in the water. Alpha shafts are far too weak to be wave hopping with a BBC.
I've ran 5 modded SBC's behind two different Alpha one drives. My current 385ci SBC makes around 475 flywheel HP and have had no problems with the Alpha. I did rebuild it with HD upper gears and a late model HD non oring vertical shaft.
Vid.....
http://www.youtube.com/watch?v=t3z0apjY1XQ