I just did this replacing my rear end and ALL suspension. I bought 2 lengths of 2x4 wood. I used 2 jack stands under the front subframe, then used 2 jack stands with the 2x4 under the rocker panel on each side as far to the rear as possible. The car was sturdy as hell so long as your front jacks are as far forward as you can get them so the back of the car doesn't lift when you remove the axle, springs, etc. I also have a couple of floor jacks I place here and there as insurance.
I'll be doing this again for my T56 swap in just a few weeks.
How I did mine too. And whenever using stands have couple large diameter oak logs to roll and/or slide under car depending on height. Also if just using floor jack to change oil have 2 old Rally wheels to slide under a-arms or frame.