"Assemble in reverse"
New rear engine seals and gaskets, new flywheel, new clutch, new slave cylinder, rebuilt torque tube, transmission leaks fixed. The drivetrain is finally ready for reinstall.
I've decided to reinstall the drivetrain in three steps. This makes it easier to get the clutch splines and the torque tube lined up correctly, as there is less mass to move around: 1) Torque tube 2) Transmission and differential 3) Rear subframe with suspension
Again, the bellhousing bolts caused troubles, with no space for my hands or any socket tools to get the threads engaged. The solution was to loop a wire around the bolts, which I could use to guide the bolts in place.
I first installed the torque tube by hand, lifting it up with me on the ground. It slid in place using only hand force, so I fortunately had the clutch disc centered correctly.
As the transmission jack/adapter was already in use for the rear subframe, I made my own custom transmission jack by bolting a wood block to a floor jack.
Only one step left, lifting the rear subframe and suspension into place. The torque tube has posts for the gear lever, which managed to trap the brake and fuel lines on the left side of the transmission tunnel as I raised the subframe and torque tube up into position. I fortunately noticed before any major damage was done.
Transmission mated to the already mounted torque tube. It slid in place using only hand force.
Finally, the car is in one piece again. By installing the torque tube, transmission and subframe separately, it was possible to do this as a one-man job with the car on floor stands. It made the weight of the parts to move around under the car manageable, so I could get things lined up easily.