MK I carrier seats

[Lynn Eades]

I dont have the info you require, and need the same for my self, so as I attempt to help you with what I can. I imagine there are quite a few Canadians around you with originals, but they are obviously shy.
The MkI* seats (apart from where "handedness" applies) are the same both sides. That means they both go up and down.
The top brackets are the same as the bottom brackets and you will find matching pairs of holes in the division plate for the lower ones.
What I have here is the original seat back covers.
From them, I would guess that the foam/padding/ horse hair etc is 1.000" (or 25mm) thick.
The overall width is 37.5mm, and the overall height is 647mm.
This includes the borders. There are 4 lift the dot things on each side and 4 along the top.
There are 5 along the bottom, but the bottom end opens for the padding to be inserted. The L.T.D things are part of the front cover, and the studs for the L.T.D fittings pass through eylets in the rear half of the cover.
I didnt have a sample so cut some flat bar, and welded some rod to it for my brackets across what I would guess is 1/2" ply.
My covers may have shrunk, but the gap between the brackets on the div plate will tell you the max width.
I cannot tell you what height the top of the seat back sits at.
If you need any more info I can do that regards the bases.
I can't remember details, but Jordans carrier thread is very informative.
Go Girl!

ps. I think the stud photo is Jordans. If you can find a source. I need them.