I have only done this one once recently (on a 1970 B) but everything about freezer bags and labelling is spot on advice. The only thing I'd add is GO SLOW. This thing weighs a lot more than I expected and even moving slowly it has the potential to injure you or damage the car, so plan out every lift and move beforehand. The workshop manual said to unbolt the transmission crossmember from the underside of the car with a jack under the transmission, then lower it slowly until the transmission was resting on the fixxed welded-in crosssmember to remove the transmission crossmember from the transmission. That worked and ensured you weren't directly under the thing while it was supported only by a jack.
If you are lifting the engine/transmission together, the balance point is pretty much right at the engine backplate. I used 2 6000 pound rated slings, one right in the gap between the pan and backplate and the other under the front of the pan. The front one doesn't really end up with a lot of strain on it, because the back one ends up taking the whole load. The transmission weighs less than the engine, but is a lot longer which is why the balance ends up where it does. I don't know what actual weight of the engine/transmission combo is, but I know I didn't want to have it land on anything other than the castor pallet it was supposed to end up on, and in
a controlled fashion at that.