The brake proportioning valve is only as far as I know on the very late UK versions as I have only seen one in the flesh on Nigel's. I believe it is 758.1.36.003.2 and is fitted to P93 A2 models. If interested I'll scan the page, I think I have a photo of Nigels also. I was toying with fitting one but it has a few pieces you would have to buy.
the 2002 price for a pneumatic spring was 576.38 euro each. I believe the latest part number is 758.1.54.501.0 (the air connection changed from M10 to M12)
ravendran667@yahoo.com.my Ravi has a few NOS rear shock absorbers which you could negotiate for.
The Pakistani ones have the folding windscreen
