DB_1-extended cab 97 style ranger (ExplorerForum) has a combined spring rate of 110lbs/in with a 200tender/250main coil setup making his secondary 250lbs/in (14"x2.5" King's)
Michael- 1st gen explorer 4 door(explorerForum) has a combined spring rate of 145lbs/in with a 250tender/350main coil setup making his secondary rate 350lbs/in (14"x2.0" Kings)
Rick has a different Coilover placement making his spring rates at the coilover much higher then DB or michael, so I didnt include his here.
Equation: Rate 1=A Rate 2= B
(AxB)/(A+B)= final rate
I asked Dave (DB_1) to measure his 14" King Coilovers at ride height. Came to be 28" eye to eye. Fully extended they are 38.5" long. This means that the shock is compressed roughly 10" at ride height. With his spring rate of 200/250, gives him a combined of 110lbs/in. This means for every 110 pounds of weight on the coilover it compresses 1 in. So if I do a calculation out that means each corner on his truck weighs 1100 pounds roughly.
Now your truck is a single cab short bed correct? so the 1100 is prolly a little high for you. He has an extended cab 4.0L truck so that weight is much more suited to my truck, but it gives you a ball park.