I plan on replacing my leaf springs in the near future and have read some threads here and on other sites.

1. Chock front wheels
2. Jack car and place jack stands under frame.
3. Place jack stands under back axle (do I need to support the differential if I do this)
4. Jack up leaf spring to reduce tension.

5. fight the rusty bolts

Any other advice or bracing needed?

You don't need to jack up the spring to reduce tension. Jacking the spring will add tension.
Support the car by the frame and keep stand under the rearend to keep it from falling out once you get the rusty bolts loose.

You may find it easier to remove the gas tank so you have better access to the shackle bolts.

You'll also find it easier to do one side at a time. That way the other spring will keep the rear where it belongs.

Safely support the car so the rear end hangs on the springs.

Jack up rear axle housing an inch or so and disconnect shocks. Let the rear hang again.

Next unbolt the shock plates so the rear is just resting on the springs.

Jack the rear up off the springs and support with stands. (car is supported with one pair and now the rear is supported with a second pair)

Unbolt the spring pocket end (ya you may start fighting rust and other issues now) and lower the spring to the ground.

Now take on the shackle end and finish removing the springs

Reverse the process to install new but install the front first and shackle end last. Don't tighten shackles until the weight of car is on the suspension.

Like Dennis said. Works great.

some more notes...

- Soak every bolt/nut with PB Blaster multiple times for several days before you start taking things apart. There are slots in the sides of the frame rails that you can use to get at the spring pocket bolts.

- when the J-clips for the spring pockets break (and most or all of them will), cut off the heads of the bolts and fish out the remnants through the slots on the sides. The easiest thing to use for cutting them is an acetylene torch, but you can also drill them out or cut them with an angle grinder.