I am attempting to pin down the reason why the rear end suspension on my ED Falcon is soft / loose.

I have Kings Lows all round and Monroe Gas shocks all round (age unsure)

Either the gas shocks need replacing.

The only other thing I can think of is the sway bar as the rear end rolls, but the front end doesn't.

When the body is pushed down on the rear it seems to spring back and feels soft.

The front is hard / tight and seems fine.

Any one had this issue and fixed it by pinpointing the problem ?

My EL has King Superlows all around and Monroe GT Gas shocks all around.

I notice the front sticks really well, but the a** end can swing out if your gentle on the throttle in a corner. Nice power slides out of corners.

I'm not really complaining, I love oversteer and its very controlled, but my car also has a lose rear too.

Any ideas?

By the subject, I thought you refering to your woman for a second....

it's always been a ford live rear axle problem, they just feel soft and slide alot, not much you can do about it besides fat swaybar, urethane bushes, stiffer springs, but then she'll feel the bumps more.
suppose it depends on what u want though.