How to Check Uni body for Straightness

While all of the above comments are FANTASTIC amounts of knowledge and advice it may be a bit overly technical. Do you have panel fitment issues? Things not lining up correctly? While keeping things where they need to be and checking some measurements is critical it's not like these cars were built with tight tolerances. I think if you have good panel fitment, no drivetrain fitment issues you should be good with minimal measurements.

No issues with panel or drivetrain fitment that I can identify. I was more worried about the body flexing when I put it up on jack stands and then welding it in a twisted position.

I really didn't know where to start or what to measure. Thanks to all of the advice I received, I definitely have a good idea now how to go about checking things out.