You only need the orange damper tube off the 240 and it has to be a GLT 262 or Turbo.

i see so i need just that damper from GLT, 262 or Turbo. Right?

Yes that is right.

You also have to cut them down to fit into the 300 leg with the special dampers.

Have you got any measurements how much that damper must be shortened (i am planning to fit -50mm springs)? And is it possible to shorten those dampers at ordinary home garage or do i need any special tools? How much it will cost if you made those top mounts? And this might be a stupid question but is it nesessary that those top mounts are adjustable, because my car is in developement stage 1 and at this point top mounts which will fit to the original mounting points are enough.

The tubes can be cut down with a hack saw or better still a pipe cutter if you can get the use of one.

The top mounts are best adjustable. Rough cost is about £100 for the top mounts. There is little point in not making adjustable as it make a big difference for little effort.

Have you got pictures of that bit of the damper where it is cut and welded piece of tube or what ever it is? And can you get better picture of that bit where adjustments and those locking thingys can be seen. Please
And thanks for being patient and answering to my questions.

No problems I will try and take some more pics of it.