I think what you are after Kevin, if I am not wrong, is a spring kit to cover up flare you are getting with gear changes. If you are not getting flare when you take off from rest but are getting it on all up shifts then you should consider adjusting the modulating pressure and not bothering with the spring kit. If you put a kit in all gears then you will probably find you need to back off the modulating pressure to not have hard shifts, but you may very well find resulting flare when moving from rest.
If you are getting it on 2-3 only then you should consider the spring kit mentioned previously. If you are getting it equally on 2-3 and 3-4 then maybe this can be improved by adjusting the modulating pressure. My understanding is that the parts in the kit are not standard parts, they have a different spring rate that will change the way the box shifts making the flare less likely. Nobody from MB will help you fit non standard parts to your car. Fitting a standard spring kit to the car will not change the way it shifts appreciably, your box is worn and needs attention other than the spring kit.
I have fitted a kit to the 2-3 shift, as I had flare just starting to develop on 2-3 only. I spent approx a year on and off adjusting both the modulating pressure and Bowden cable to compensate for a heavier spring – my box was not quite worn enough. Between the two I now have the box shifting very close to perfect, BUT I can only just feel the shift 2-3 over that of 3-4 due to the spring kit. I did not need to replace more spring kits ( if I did it would have been box out to fit them at which point it is better to rebuild the box) it is possible to tune the box so the combination of a harder shift spring kit and softer factory spring shift are very nearly impossible to detect. Maybe the 2-3 is wearing out more now coming into the firmer kit range nicely.
I think the fix with the kits is something owners and mechanics came discovered/came up with, it is not a MB sanctioned repair method, that’s why it will be impossible to formally get the up rated spring kit numbers for your box from MB – not unless they know about your problem and know exactly what to fit to your box and don’t mind recommending it to you as a favour.
I take it you have looked closely at vacuum leaks (=harder shifts generally) and other issues the box may have. Isolate and sort these first.
If all else fails, The Classic Centre in Germany will rebuild your box from about 2500 euro.
Mercedes-Benz Classic - Spare Parts - Overhaul of Automatic Transmissions
It really will be good as new!!
Let us know how you get on...........