Hi realneal,
I have some info for you. I have only ever been in one 1000SEL which was owned by someone who bought the car from a prince of saudia arabia. I will work on getting pics and specs for you as soon as I can, and post them for you.
In regards to your questions:
a) I don't ever recall seeing a mooroof on a W126 as a factory option. I'm not saying that it wasn't available though. Most options on the 1000s were custom anyway. Like I said, I will get you the info.
b) More than likely the suspesion is AMG... or sports.
c) I strongly believe all the suspension and normal-wear parts are standard MB.
d)I've enclosed a pic of a climate control setup in a W126. Does it look like this one?
e)I wanted to do the ABS conversion for my W201 and my mechanic said it wouldn't be a problem as long as I din't have to buy all the parts new
f)The 80s cars were well known for their chrome trim everywhere, bulky aero kits, and bulky and lots of everything. If you look at these cars in Germany you will know what I mean.
f) I know someone once put a 4spd in a W126 500 and it seemed to work fine for him. I even heard from someone that saw a W140 600 in France with a manual transmission. He swears he did. He looked in the car to see the interior and noticed that there was someone in the car....he couldn't see well through the tint (the car was black on black with tint). He had to step away as the passenger was not too pleased to see him.