some springs are a tad longer on drivers side some are same height but poundage a bit more happy days
Different rate springs on the same axle? should have about the same effect as mixing cross ply and radial tyres. Only the length should vary between the springs on an axle, not the rate.
To remove both springs, why not jack the body up and remove the spring on one side, lower it down to the bumpstop and the repeat for the other side?
As for the differeance in spring length, the depends on just which rate springs you have fitted. Typically the differance is about 1/2" on land rover springs if they are handed.