When I took the bucket apart to rebuild it the front struts had the spacers fitted. My car is a RHD UK supplied car. The spacers are approx 15mm thick, but I would need to confirm (If I can remember where I put them :roll: )
It also had 3 domed nuts per strut with washers fitted, so If the spacer was left out then the nuts would not tighten up.
At the rear it had rubber spring "pads" or "seats" both top and bottom. from memory they are approx 10mm thick.
Reading the official workshop manual, Europe only, there appears to of been various rear pad and front spacer thicknesses used, along with different spring lengths and poundages.
Why I don't exactly know but I would suspect it would depend on the supplier at the time and quite possibly to compensate for variations in the bodyshell build process, application, customer requests, preference, market supplied etc etc.
However I do know I made sure I labelled all the parts to ensure they went back in the right place just in case they were used to "true" the ride hieght up!
Malc