Axle Upgrade

Hey there, I had a few questions about axles. First off I've recently turned my 340 into a 416 in the neighborhood of 510 hp. I know that the stock 37 year old axles will not hold up forever. I would rather address the problem now before I it bits me in the butt at the strip or at a cruise night. First question is what brand are y'all using (moser, strange, ect.)? Granted I'm still a youngin' and don't know everything about axle changes, but don't you have to change the differential too; or is that only if you go with more splines? And finally, where did you get them from? This kind of related to another question I had aboout torque converters. Is there any other place to order B&M Holeshot converters rather than jegs or summit? Sorry for the essay but stuff just kept coming to mind.

Thanks
Kyle