Sagging Rear Offside Suspension

The rear springs on my SWB S3 were originally 7 leaf springs (which I believe are the heavy duty springs for a lightweight), and the ride was awful, so following a recommendation, I removed the springs, stripped them down, wire brushed the rust away and greased them, before putting them back together with leaf 3, 5 and 7 left out.

The ride is far far better, but now I am parking it on a flat driveway, I have noticed it sagging to at the drivers side by about 6cm.
I didn't think that the rear springs have a specific side, but I could have put them back on the wrong side when taking them off to refurbish them, if they do.

Looking at the springs, the drivers side rear spring is siting much flatter than the passenger side spring, and the drivers side rear shackle has rotated slightly to take up the increase in the effective horizontal length of the spring, due to it sagging.

The spring rate was calculated for the springs with the 3 leaves removed, and they should be plenty strong enough for the weight that is being carried (I never have anything heavier than 2 dogs in the back).

Are my springs knackered, and in which case, what springs would you recommend as replacements, or could something else be causing the rear corner to sag?

I'm not sure about lightweight springs but normal 88" ones are handed. Also, when refitting you need to make sure everything is level before doing up all the shackle pins.

I'd say you probably need to swap them. Also, before tightening up next time - leave them a bit slack and drive over a few bumps to settle everything then load up the back with a few bags of sand until you're happy with the side-to-side and front to back alignment before tightening the pins. With metalastic bushes you need to pre-load them a bit before tightening and that will try and pull everything true and make for a better unladen ride.

At least it should all come apart easily enough If you just did it...

When you have them off compare the curves.

They probably only needed the strip and grease without leaving any leaves out. As Blackburn says compare the curves in case you have mixed them up.

did you tighten shackles with a 142mm gap between axle and chassis?

Thanks for the suggestions, I didn't realise the rear springs were handed - thought that was only the front.

Well, I swapped the springs and there is no difference! I can force it level by following the guidance in a previous post and overcompensating, but this doesn't seem like a sensible solution.

I then measured bolt centres on the spring mounts as best I could and got 1150mm per side - one side might have been 5mm longer than the other, but can't be 100% accurate without the end of the tape measure being held by a helper.

I haven't done the maths, but even with a 5mm difference in spring mount length, the shackle would not rotate would anywhere near enough to effect the height of the vehicle this much.

My three thoughts as to what else could be the cause are:
1. The rear 1/4 chassis (which I can see has been replaced in the past) is not on straight and is lower on one side than the other.
2. The springs that a previous owner put on are both for one side (ie both passenger side springs).
3. The removal of spring leaves has more of an effect than I calculated with the additional weight on the dirvers side.

I'm not about to go cutting the chassis and rewelding without being 100% sure that this is the problem, and I can't stretch to new springs at the moment, so any suggestions for a way round this, or what else might be the cause, would be most welcome.
All I can think of is extended shackles on the low side to raise the height on that side of the vehicle.