what i would do. if you have a engine crane. take the whole thing out (engine/tranny). this will give you the chance to clean up the engine bay and clean the motor up. you can also make sure all the other under hood item are as they sholud be. hook up the new tranny and make sure all is good and then back in it goes. easy stuff.
I pulled my engine and transmission out of my 69 in my backyard.
Had the front supported with jack stands where the lower control arm mounts. I would say the jack stand was about a foot and a half from the bottom to its top where the car would sit.
Then I raised the rear up to make it about level.
Make sure you buy a quality load leveling device. I picked up a cheap one at Pep Boys and it barely worked. It would bind when trying to angle it steep to get the engine and trans out together.
If you are just pulling the transmission without the engine You would need it high enough to get the trans in and out from under the car + whatever room to work. Hard to give you a measurement for this way so I will just say as high as you can get it. Especially if the bell housing is coming out with it, thats the biggest part. If you pull the trans from bellhousing then the bellhousing from the engine (if needed) you wouldnt need to get it as high because you could just flip the housing over on its side so it would aonly be about 7 inches tall vs whatever the diameter of it is a foot or more?
I initially installed the AOD in mine with the engine from above, but had to R&R it later (twice) and it came out from underneath with the car up on four jack stands.
I removed the saddle from my floor jack and bolted a 12 x 12 piece of wood to it. The jack stands didn't give enough clearance to roll the trans under the car with it on the jack. Getting it lowered and raised and lined up was easy. The hard part was getting it on and off the wood platform from under the car.
Best advice: get a buddy that can bench at least 175 lbs.
I've done multiple trans swaps with the engine in. Jackstands at full extension and a transmission jack make it easy. I even did my C4 to T10 then T10 to T5 swaps with this method. A few blocks of wood helps if you don't have a transmission cradle for your jack.
I agree about the bench-pressing part; you'll need it to do final alignment. The T5 and C4 were easy. The cast-iron T10 not so much.