Cool, sounds like you got a plan along with the materials and equipment needed to fabricate it all. Got a question though.
Why are you cutting your stock A-arms up when you intend to build them from scratch anyway after the design is finalized? Wouldn't it be easier (or safer?) to leave your stock a-arms alone, so you'll have a working bolt-on set with proper geometry to serve as a model for your target geometry? Think about how many times you may wish you could go back and look at the stock geometry and measure for this or for that, or check the angle of this or that other thing that you forgot to take into consideration while planning... Why not just design them both and build them from scratch?
I can see how easy the CV shafts will be to lengthen... just chuck them up in an engine lathe and cut them off clean and square some place along their length that is ideal for a length of thick-wall chrome-moly tubing to be welded over those stubs. Weld tacks could be put in place while chucked in the lathe too, so that the shaft remains perfectly true in its rotation when welding is completed.
Great project idea you got going on here! Sounds like a lot of fun!!!!