"straight span mm (in) 1196.5-1,203.5 (47.106-47.382)"

is the distance eye to eye (string method mentioned earlier) of a stock new spring. You want the measurement from that string down to the center pin of your spring pack. I can check to see if my mounted spring dimensions (eye to eye) are the same as the straight span, and then I can measure to the center pin. But if I had to guess I think my measurement would be a little off since the springs are still on the truck and under tension.

If you had one of yours off the truck you could see how far off it is compared to the straight span measurement.

Z