Rear Axle(s) Play

It's not play, it's the spring being completely unloaded with the car in the air and you being able to load them a bit by yourself.  I could fairly easily move both sides of mine up a couple of inches when it was jacked up.  As to why the amount is different from side to side, I don't know but unless you are aware of a real problem when driving I wouldn't worry about it.  If there is a problem, the first place I would look would be one or the other shock absorber.  You could try swapping them from side to side to see if anything changes.

I suspect that your torsion bars might not be equal side to side in the rear.  
Drive around the neighborhood, then return to your garage and park normally inside your garage where it’s flat and the suspension is settled.

Go out to your car with a tape measure and measure, in a straight vertical line from the ground straight up across the center of the wheel hub to the top of the wheel well opening, to see what the vertical distance is on both sides.  Record the measurement on both sides and report back.

I suspect that you’ll see the driver’s side will be higher than the passenger side (or....  I may be all wet!)

Quit lookin for things to be wrong and drive Meade. Just kidding. I doubt this is anything that needs to be addressed.

Can we please stop telling people to measure from the known-to-be-inaccurate-side-to-side-fenders? Fender lips are easy to get to and see, but you'll probably end up with an ill-handling car by using them.

Measure from a hard point on the pan, such as the bottom of the beam in front and the bottom of the torsion bar caps in the rear.

So there you go, Meade.   Expert advice from the leading experts on the site.

They've been in the forefront of helpful information for an age, now, and have shown us ways to improve our cars with the very best available products out there.   You can't go wrong listening to them.

The rest of us are just posers.  Don't pay any attention to us.  Especially me, I guess.  I don't even have "Hoover Mod Bits".