With the car on level concrete, look at the rocker panels and their relationship to the concrete. They should be parallel, unless the front bars have been adjusted "down" or "up". Look at both sides.
Then, get on the concrete and look at the dimension between the lower control arm bumper and the crossmember under the oil pan. They should be equal. Don't worry about "inches", you can get a good idea just by using your fingers (vertically) in that dimension.
As for the rear leaf springs, with the car on a drive-on "muffler shop" lift, measure the distance between the rack and segments of the leaf spring, about 2" between the measurements. Compare the results from each side. You might discover that the main leaf has a bend or sag, comparing them side-to-side. It can be "hidden" until you find it, then it'll be very obvious.
Age and "wear" on the front eye bushings and the rear shackle bushings should be about the same on both sides. AS should be the iso-clamp rubber insulators which cushion the leaf spr assy between the rear axle mount clamps.
Of course, any time you're under the car, at ride height, make sure the vehicle is in "P" and/or with the parking brake firmly applied!
Let us know what you determine.
CBODY67