If your going 600-650hp a Dana would end your worries...period.If all you can find or afford is a 9 inch?Build whats best for you.Maybe see if you can find a .489 case and build it with a spool(4.30,s)My narrowed 8 3/4 .489 case with spool and Strange axels has held up well so far.If it starts breaking,I will go Dana,8)