seems like a lot of work and $$$ to spend to only gain bolt in axles.
as far as fitting wider wheels with different axles- the same width wheel will fit in the stock wheelwells no matter how long the axle is. if a 5" backspace fits with the stock axle, then a 6.5" backspace will fit with an axle that's 1.5" longer.
i'd spend the same amount of $$ and just get 9" Ford axle flanges welded on your stock housing that allow you to use any GM rear brake setups. get a stronger set of aftermarket axles with Ford bearings, and go play without worrying about breaking axles.