checking rear end housing straightness

Honestly I would direct the energy to finding a stronger rear end like an 8 3/4 . By the time you verify straitness and buy gears/ pay for the to be set up you are 3/4 the way to an 8.75 . Since you want 4.10s I have to assume you are making some power and plan on using that power .
I recommend 8.75 because both housings and pumpkins are readily available ad you won’t have to pay to get the gears set up if you buy a functional pumpkin . A good ford explorer rear end would work as well but I am not sure about gear availability.