Welding a back brace on a 8 3/4, any advice??

They probably are indeed off center (tubtar can verify) but the axle isn't. If a housing is bent, you can either straighten the housing or relocate the housing end using a gage to locate center relative to the 3rd member. Either way the axle, 3rd member, and car don't know the difference.

Yep. I welded the back brace on and it definitely moved. Bob Fuller at C&F narrowed it and told me how I could have avoided this ( a fixture ) , but the axle ends are true to the carrier bores and it's all good.
I did weld in short sections , but that sucker was either bent when i started or really moved around.

I didn't consider the other, because the fabricated housing was stronger and cheaper. I got a heck of a deal on the housing. I had placed my order for a bare fabricated housing with back brace on Tuesday, Wednesday morning I got a call from Moser asking if I was interested in a housing that a customer ordered, and then cancelled the order (leaving them with a custom housing that no one wanted). It was back braced, powder coated, with perches in a weird location....anyway, we struck a deal, since I would have to do some cutting and welding to make it work (I got it cheaper than what I had ordered...with the powder coat upgrade:D). Got it cheep and FAST!! It showed up on my door step Thursday!! That's a 2 day turn around time :cheers:. I will definitely use Moser again in the future...GREAT customer service.

Ya gotta love it when a plan comes together. :D:D