OK.
As yours is a 90 then all the springs are the same diameter. 110's and 130's etc have larger diameter coils at the rear.
Ok you should have 2 rates i.e 2 springs with a higher Lbs/Inch for the rear of the 90. from memory Standard are 215Lbs inch and the fronts (diesel and Petrol except V8) are 170Lbs/inch. Roughly.
Once you have established the 2 different rates then the longer spring of the 2 goes on the drivers side. It is normal for a 90 and Series (leaf spring) to lean to the passengers side this is bacause the slightly longer springs are fitted to the drivers side to counter act the driver and fuel tank. Similar can be said for RR and Discos although some people shim them up level with plastic shims and they look awful leaning over when being driven. It could be that the springs that are longer are slightly longer mabe up to half an inch these could be the drivers fronts and rears but without any info of what kit you have we can not really help.
It may be that you have a "lift kit" this may come in many forms I will explain a few here.
Longer softer springs, Great offroad not good for weight carrying or towing. (I use these approx 3 inch taller springs that settle due to being softer to about a 2 inch lift)
Same length stiffer springs, good road handling not so good offroad.
Longer stiffer springs, could be argued better road handling, good for weight but not so good offroad.
What Kit do you have from that we can establish what you got. Jai