need to use uprated shocks and springs on the back of the jwrc kitted fiesta

i already run a kw coilover kit but the huge arches even on a full drop still have a huge gap between wheel and edge of the arch

ive measured the drop of what i want and have found the dampers that will do the job but how do you measure the springs

when it says spring free length -this would be the length of spring when uncompressed

most you you max spring travel

but its the spring rates that i dont understand ilbs/ins

any help would be much appreciated