D'oh! I forgot to take pics! I'll take some tomorrow and post them up.

I'm happy to help anyone figure out how to install the seats, if anyone has any trouble.

The w126 seats do have a taller bottom, so at its lowest setting, it won't be as low as the lowest setting on the w123 seat. It's the seat bottom, not the rails. The difference is about 1" unloaded. Also consider that one sinks further into a w123 seat than a firm w126 seat. I am used to driving sports cars so I liked my MB seat low, and the w126 seat doesn't go that low any more. My head doesn't hit the ceiling, and I'm 5'10". Tomorrow I'll measure how much head room I have.

Using the springs out of a w126 seat bottom into a w123 seat bottom is a nice trick. Have you tried the springs for the seat back? My w123 seats were worn out in the bottom and the back equally - I would not have been happy with just fixing the bottom springs.

Yes, you can mount the w123 rails onto the w126 seat, if you want to have the full-on w126 seat. It will let the seat be manually adjusted for forward-backward sliding, and height adjustment. However, you will need to wire some sort of custom switch to the seatback motor directly, so you can adjust the forward-backward lean of the seat back. You might also want to wire a switch for the headrest.

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'82 300TD
'77 6.9
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'87 Porsche 944 turbo