Sure! You can do all that at once. You can strip the car to the frame too, but it'll take longer.
I recommend taking the engine & tranny at once, it's not much work disconnecting the tranny from the chassis and pulling it all out together. You can pull them out together if the car is a bit too low, I've done it myself. I just put a floor jack under the tranny mount area to keep it supported while you pull the whole thing out. I'd suggest putting a block of wood or something similar between the jack & tranny, to avoid damaging anything.
With the front end in the air, it can be impossible to get a floor jack under the gas tank to get at the rear axle. If you don't want to lower the front end to get your clearance, you might be able to slip a floor jack in between a rear wheel and the gas tank and get it under the differential. I was able to do that once, but it was a tight fit.
Part of the answer to all this is how much time do you have? If this is your daily driver, I'd recommend leaving the rear axle until later. But if you have all the time in the world, go ahead and drop the rear axle at the same time.
Urban96 has a point. The more you do at the same time, the more you have to troubleshoot at once if you have a problem. It's usually better to do one thing at a time then test it out.
Why do you want to drop the rear end? Do you have a built one to replace your stocker?
)
