A thing that I do on mock up suspension stuff-I figure out suspension height , tire radius, etc and then make/install some tubes with ends that mount to the shock absorber mounts at the length of ride ht----that keeps suspension static points at heights I'm working around and want to keep constant-------

I then support the chassis/frame frome that area at the rear and one point centered at front spring mount point in the front so there isn't any cross bind in the body mounting

Rule of thumb to remember that is helpful in navigating the world is one in sixty equals one degree--it also works with suspension serup----drive shaft/u-joint angles, caster/camber angles, etc--------

A good point for referance on axle squareness (front and/or rear) is a central point at trans mount crossmember--------

I also use mostly 9 inch ford rears so I have a pumpkin with a pinion shaft housing set up for diameter of engine main bearings and use a thickwalled tube that diameter to establish drive line angles---and that dummy engine with that 3/4 wall tube is heavy but very stabile-----