68 K10 Rear Springs

[68C20]

I have a 68 K10 long bed stepside that i am trying to replace the rear springs and lift the truck at the same time. I am getting mixed answers as to the actual length of the original springs. My originals went to the scrapper a long time ago due to broken springs. I am hearing that my truck should have 52" springs like the 69-72. These springs are way to short. Then I am read that it has 56" springs, tried them and the center pin is off by several inches. Now I have two sets of rear springs and still do not have my axle attached to the truck. I have contacted a spring maker and was told that the springs are actually supposed to be 58" eye to eye with the center pin in the center. Does anybody actually know where I can find out what my truck is supposed to have lengthwise for springs and where to buy springs? Really confused and wishing I hadnt thrown away the broken springs when I disassembled the truck.