8 3/4 gears

Hello, all. I have a spare 8 3/4 complete rear end for my '70 Swinger 340. I'm building a stout 408 for her, and it's time to consider the rear assembly. I have a small yoke 741 with a 3.23 SG rear assembly. I have a couple of questions:
Can I replace it with a 742 or 489 SG, or is this overkill?
All the rear disc conversions seem to require 15" wheels. I know Summit has 15" wheels in the SBP, is this the way to go?
Green bearings, or Timken tapered?
Will my stock axles handle about 480HP at the wheels, or do I need to upgrade?
I'm making this like a FAST car, I want to look stock if you pull up next to me.
Thanks to all ahead of time for the fountain of knowledge about to come. Paul.