So you just need to pay someone to weld the threaded sleeves on - but do you have a set of springs at the height you want?

Also it would be worth checking if the springs you have fit the adjustable height platforms.

I have a set of threaded sleeves and platforms that fit a 60mm ID spring - when standard Datto springs are around 80mm. So the standard Datsun springs wont fit on the 'sports' spring platforms.

Worth a look before you get them welded on.