the versailles rear is a heavy duty housing, big axle tubes(3" ) and 'big bearing' ends. It is kinda heavy, and probably overkill for the power you're making. You might be better off getting a regular 9" housing and getting an aftermarket disc brake kit. I think Wilwood and Baer make kits that sell for $500 or so. I think its a solid rotor though(kinda thin), but it has aluminum calipers-so it should be lightweight if that is a concern. If you want durability you'll need to upgrade axles on any factory rearend, so don't hold that against the Versailles. Even though I think mine were the same as any other 9" axle, didn't notice any weird taper.
Personally, when I swapped form a 8" to the versailles with the same gear ratio I only lost .04 seconds(average) in the 1/8th mile, so no biggie. I'm thinking of getting mine narrowed a little and I'll probably switch to either Wilwood or Baer discs, but I don't drive it on the street much.
There are also several 'junkyard' rear disc conversions using Mark VII or Explorer parts, should save a little weight plus you'd have OEM reliability and parts availability.