Putting it that way, yeah, that would make a noticeable difference. Now I rechecked the book, here is a condensed version:
A & B springs can be used to compensate for uneven vehicle weight distribution. Springs marked "A" have a greater camber height than springs marked 'B'. 'A' type springs are generally fitted to the driver's side and 'B' springs to the passenger side.
A & B springs are used to compensate for uneven vehicle weight distribution. 'A' type springs are generally higher in free height than the 'B' spring. Individual coil specifications are listed in the back of this publication.
Then we have the WK Part numbers from page 15:
Front (to 40KGS): 2990
Front (41 to 100KGS): 2991
Rear Medium Load: 2992
Rear Heavy Duty: 2993
What struck me about this is that:
1) Straight out of the book OME lists these part numbers for both 2005-2010 WK and 2006-2010 XK.
2) They are also listed for both models in Petrol (gas) or Diesel.
3) OME states front lift at 50mm, and rear at 55mm.
4) The "A" and "B" Spring notation is absent here.
5) There is no "Medium" or "Heavy Duty" reference for the front, only specific weight carrying capacity rates. Only the rear springs are referred to as such, but without the rates.
6) I find it a bit strange that only two choices in spring rate can cover two different vehicles (as far as vehicle weight), with two different powertrains (Gas or Diesel), across at least four years production time. Given that the WK and XK are the same chassis, I got it. But the differences in curb weight and various options plus possible minor design changes and the different possible variations in drivetrain selection and therefore weight, to me, seems like there should be a few more spring rate choices, But, I dunno. I don't design and build this stuff for a living. I'm just stating what pops out to me.
Then we get to page 129 (See attached):
On the chart it lists for these part numbers the same static height (free) for the front springs, but different ("A" and "B") static heights (not load ratings as I had previously mentioned. Doh! I had to look at it closer!) for the rear springs. Another neat thing here is it also lists what the factory spring rates are. I find it interesting that OME only lists one factory rate for the front, and one for the rear. There are a great many MOPAR part numbers for each location for factory springs on these vehicles.
After looking at this again, my guess is the higher (both standing fresh out of the box on level ground right next to each other) rear spring goes on the driver side.