Alright, I took some pics. The only digital camera I have at the moment is my cell phone, so I apologize for the quality, but it gets the point across.
Here they are. The front height is lowered as much as it can go. The rear height is raised a little bit.
You will need to figure out where to route your wiring and where to put the switch. Here you can see how long I made the wiring and where (about) the switch will sit. The orange wire will be rerouted under the console & dash, and go to the battery + terminal.
This shows the headroom available. I am 5'10", and I measured 3" of space between my head and the roof.
Here you can see the W123 seat belt receivers, which you need to use. They are a little recessed compared to how they are on W123 seats, but they still work fine.
That gold bolt is the one you need to remove in order to swap the W123 seat belt receiver onto the W126 seat's bracket. After this mod, the W126 trim pieces won't fit anymore, so I left them off.
Wiring goes under the carpet...
You will need to cut a notch in the W126 seat's carpet trim piece, in order for the wiring loom to be able to squeeze between the seat and the floor (see pic).
With the wiring loom hidden under the carpet, and the orange wire routed to the battery.
On the driver side, the switch is on the other side, next to the center console. However on the passenger side, I sometimes put my drink there, so I chose to put the switch on the door side. I'm planning on making some kind of mounting for that switch so it doesn't move.