Just so you know ... I thought this was a simple operation but apparently the whole assembly has to be taken out and placed on clamps.
The thing moves when it's being welded and if it wasn't held in place off the vehicle it'll come out unaligned.
I built my rear end up with stronger axles and differential, the next thing I want to do is get the tubes welded but having to drop the assembly is a bit left to be desired.
But to answer your question, Brad's Custom is probably the best bet but Marysville Speed is another good one if you're up north.